• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.225-230
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• 2001

Hydrostatic bearings have been applied to high precision machine tools and instruments due to their high stiffness, high damping and excellent guided motion straightness. In this paper, we present a procedure for design and test of a high precision press with linear hydrostatic bearings. For a hydrostatic bearing set designed manufactured, measurements were made for the motion straightness, repeatability and bearing stiffness. They are found to be 1.36${\mu}m$/100mm, 0.19${\mu}m$/100mm and 1,261N/${\mu}m$ respectively. With some experience with the hydrostatic bearing, design aspects of the precision press is discussed.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.4
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• pp.236-241
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• 2001

Teach pendant is the most widely used means of robot teaching at present. Despite the difficulties of using the motion command buttons on the teach pendant, it is an economical, robust, and effective device for robot teaching task. This paper presents the development of a force/moment direction sensor named COSMO that can improve the teach pendant based robot teaching. Robot teaching experiment of a six axis commercial robot using the sensor is described where operator holds the sensor with a hand, and move the robot by pushing, pulling, and twisting the sensor in the direction of the desired motion. No prior knowledge of the coordinate system is required. The function of the COSMO sensor is to detect the presence f force and moment along the principal axes of the sensor coordinate system. The transducer used in the sensor is micro-switch, and this intuitive robot teaching can be implemented at a very low cost.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.548-550
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• 2010

The droplet motion on a flat substrate with contact angle hysteresis is studied by solving the equations governing the conservation of mass and momentum. The liquid- gas interface is determined by an level-set method which is based on a sharp-interface representation for accurately imposing the matching or coupling conditions at the interface. The method is modified to treat the dynamic contact angle at the liquid-gas-solid interface. The computations are performed to investigate a droplet impact and merging pattern on a flat substrate to find a optimal condition in a micro-line patterning process. The effects of dynamic contact angles on droplet motion are quantified.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.334-337
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• 2003

In this paper. we introduce a novel actuation method based on dielectric elastomer. Along with basic principles of actuation using dielectric elastomer a new design of actuator is discussed. The proposed design has advantageous features in reduction in size, speed of response, ease and ruggedness of operation. Using the actuator. a three-degree-of-freedom actuator module is developed, which can provide up-down. and two rotational degree-of-freedom motion. In the application of the proposed actuation method, a micro-robot mimicking the motion of an inchworm is developed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1166-1174
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• 2000

In this paper, we introduce a positioner based on magnetic levitation to eliminate the friction which is the most severe effect to limit high resolution on the micro level. Differently from existing electromagnetic device, the proposed positioner consists of air core solenoid and permanent magnet. Although the combination produces small magnetic force, it is suitable for realizing micro motion repeatedly without the accumulation of error because there is no hysteresis caused by ferromagnetic materials, no eddy current loss, no flux saturation. First, the approximate modeling of stiffness and damping effects between the magnetic elements is made and verified experimentally. Then, we have formulated the dynamic equation of one d.o.f magnetic levitation positioner using linear perturbation method and discussed the necessity of optimization for the chief design parameters to maximize the stability performance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.4
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• pp.338-346
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• 1981

Honing, lapping, polishing and superfinishing are applied for a precision machining to finish the metal surface, but these precision machining are micro-cutting by hard and micro-abrasive grains. Frictional machining is the new method to finish mirrorlike surface without using those abrasive grains. The frictional machining produces high pressure and high temperature instantly by compressing a tool material against the metal surface in sliding motion. The metal surface is given plastic deformation and plastic flow by the above mentioned frictional motion, but the surface roughness of the metal surface is influenced by physical and chemical reaction in surrounding atmosphere. Therefore, the atmosphere around the metal optimum atmosphere in the frictional machining. The part 1 of the study was performed in liquid atmospheres. Diesel oil, lubricant, grease, lard oil, bean oil and cutting fluid were used as such atmospheres. Medium carbon steel SM 50 C was used as a workpiece and ceramic tip was applied as a frictional tool. The result of the experiment showed characteristic machining conditions to generate the best surface roughness in each atmospheres.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.407-410
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• 2006

This study describes a simulation of two-dimensional bubble forming and motion by the Lattice Boltzmann Method with the phase field equation. The free energy model is used to treat the interfacial force and deformation of binary fluids system, drawn into a T-junction the micro channel. A numerical simulation of a binary flow in a cross-junction channel is carried out by using the parallel computation method. The aim in this investigation is to examine the applicability of LBM to numerical analysis of binary fluid separation and motion in the micro channel.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1487-1491
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• 2008

Detailed knowledge on the motion of blood cells flowing in micro-channels under simple shear flow and the influence of blood flow is essential to provide a better understanding on the blood rheological properties and blood cell aggregation. The microscopic behavior of red blood cell (RBCs) is numerically investigated using a fluid-structure interaction (FSI) method based on the Arbitrary-Lagrangian-Eulerian (ALE) approach and the dynamic mesh method (smoothing and remeshing) in FLUENT (ANSYS Inc., USA). The employed FSI method could be applied to the motions and deformations of a single blood cell and multiple blood cells, and the primary thrombogenesis caused by platelet aggregation. It is expected that, combined with a sophisticated large-scale computational technique, the simulation method will be useful for understanding the overall properties of blood flow from blood cellular level (microscopic) to the resulting rheological properties of blood as a mass (macroscopic).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.389-396
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• 2001

Direct numerical simulation of bubble growth and merger process on a single nucleation site during partial nucleate boiling is performed. The equations governing conservation of mass, momentum and energy are solved using a finite difference method combined with a level set method for capturing the vapor-liquid interface. The level set method is modified to include the effects of phase change at the interface and contact angle at the wall. Also, a simplified formulation for predicting the evaporative heat flux in a thin liquid micro-layer is developed and incorporated into the level set formulation. Based on the numerical results, the bubble growth and merger pattern and its effect on the heat transfer are discussed.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.858-864
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• 2017

This study aims to restrain free conducting wire-type particles which are commonly and dangerously existing within DC gas-insulated transmission lines. A realistic platform of a coaxial cylindrical electrode was established by using a high-speed camera and a partial discharge (PD) monitor to observe the motion, PD, and breakdown of these particles. The probabilities of standing or bouncing, which can be affected by the length of the particles, were also quantitatively examined. The corona images of the particles were recorded, and particle-triggered PD signals were monitored and extracted. Breakdown images were also obtained. The air-gap breakdown with the particles was subjected to mechanism analysis on the basis of stream theory. Results reveal that the lifting voltage of the wire particles is almost irrelevant to their length but is proportional to the square root of their radius. Short particles correspond to high bouncing probability. The intensity and frequency of PD and the micro-discharge gap increase as the length of the particles increases. The breakdown voltage decreases as the length of the particles decreases.