• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.79-82
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• 1997

The current from the feed motor of a machine tool contains substantial information about the machining state. There have been many researches that investigated the current as a measure for the cutting forces. However it has not been reported that indirect measurement of the cutting forces from the current of the feed motor at rest is possible. The cutting force normal to the machined surface influences the machined surface of the workpiece, which makes it necessary to estimate this force to control the roughness of the machined surface. But the unpredictable behavior of the current prevents applying the current to prediction of the cutting state. In this paper, empirical approach was conducted to resolve the problem. Also parametric adaptive and fuzzy logic control strategies are applied to the force regulation problem. As a result, the current is shown to be related to the accumulation of the infinitesimal rotation of the motor, and besides the unpredictable behavior of the current is shown to be caused by the relationship. Subsequently the relationship between the current and the cutting force is identified, and it is presented that control of machined surface using the current of the feed motor at rest is possible.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1121-1124
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• 2004

Aging test to estimate life property of polymer insulator is executed through several international standard such as IEC 61109 and CEA tracking wheel test, but is not getting clear conclusion yet. There are two methods in the diagnosis method of polymer insulator such as off-line and on-line. The diagnosis methods in off-line are external condition analysis by the eye, contaminant analysis on surface, surface analysis, pollution withstand voltage test, power frequency flashover voltage test, lightning impulse flashover test, tensile fracture load test and flexural load test. The diagnosis methods in off-line most are the method for virgin and last aged sample. However, the diagnosis method in on-line is method that can be evaluate sample state as progressing continuously aging test in beginning, The diagnosis method in on-line is arranged as following: leakage current measurement, electric field, surface state investigation, thermal image, emitting light measurement and then so. In this paper, the tracking performance of polymer insulator with salt solution which is added surface active agent. The diagnosis of insulator sample has been analyzed by leakage current and visual examination.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2019-2028
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• 1997

It has been well established that resistant force and wear that occur during rolling motion depend on several factors such as material type, hardness, subsurface microstructure, applied load, and speed. The purpose of this work is to investigate the effect of microstructure and the state of deformed layer on the rolling contact characteristics in dry and lubricated rolling contacts. The results of this work show that the rolling resistance behavior depends on the state of the deformed layer. Also, lubrication can reduce the plastic flow at the surface but may still have an effect on the subsurface strain. The cross-sectional view of the microstructure shows that surface traction has a difinite effect on the morphology of the surface region. That is, significant slip seems to have taken place between the ball than those of the dry rolling case. The surface generation effects were significantly less compared to the case of dry rolling contact.

• Journal of the Korean Society of Safety
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• v.20 no.1 s.69
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• pp.94-100
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• 2005

The plasma, ionized gas state, is generally composed as the 4th state in the universe. Generating the plasma artificially has been studied by spending energy and it has been applied so much in human's life. There are several merits to modify the surface of polymer using plasma. Above all, plasma maintains the properties of polymer itself, but changes the properly of polymer surface only. Also, it is the environmentally fraternized because there are no waste processing from organic solvent. Furthermore, it is possible that continuous automated-processing in case of high-pressure plasma. Therefore, we have tried the reforming of surface to rise the adhesive strength between the material of polymer, and have experimented rising the adhesive strength through peel strength by virtue of processing time and using gas, of course, confirmed the change of polymer surface through measuring the contact angle analysis and scanning electron microscopy(SEM).

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.349-365
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• 2017

Graphene has attracted a lot of attentions due to the unique electrical and optical properties. Compared with the noble metal plasmons in the visible and near-infrared frequencies, graphene can support surface plasmons in the lower frequencies of terahertz and mid-infrared and it demonstrates an extremely large confinement at the surface because of the particular electronic band structures. Especially, the surface conductivity of graphene can be tuned by either chemical doping or electrostatic gating. These features make graphene a promising candidate for plasmonics, biosensing and transformation optics. Furthermore, the combination of graphene and metasurfaces presents a powerful tunability for exotic electromagnetic properties, where the metasurfaces with the highly-localized fields offer a platform to enhance the interaction between the incident light and graphene and facilitate a deep modulation. In this paper, we provide an overview of the key properties of graphene, such as the surface conductivity, the propagating surface plasmon polaritons, and the localized surface plasmons, and the hybrid graphene/metasurfaces, either metallic and dielectric metasurfaces, from terahertz to near-infrared frequencies. Finally, there is a discussion for the current challenges and future goals.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1590-1592
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• 2000

The time to tracking breakdown of treated filled specimen is longer than untreated filled specimen. And, after the RWDT, the surface of specimen by adding untreated filler appeared heavy erosion. It was found that the addition to surface treated filler. the better tracking resistance. In the RWDT, the breakdown specimen is not affected by the dry flashover voltage. despite the fact that the surface degradation of tracking test has different state on each specimen. This suggests that wet flashover voltage play an important role in evaluating of tracking and erosion on the surface degradation in tracking test. And, the flashover voltage of specimen under wet conditions are greatly affected by the salt concentration and degree of degradation by the RWDT. Because of hydrophobicity and degree of degradation by the RWDT, the flashover voltage of treated filled specimen is higher than that of untreated filled specimen. Different types of specimen may have different hydrophobicity and their surface state under contaminated conditions may not be the same. It is assumed that this phenomenon is related to the decrease in hydrophobicity of the surface of the materials.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.774-778
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• 2004

The atomization process of a circular $SF_{6}$ liquid jet issued into an otherwise quiescent, high-pressure $N_2$ gas was observed to explore the breakup mechanism of liquid ligaments involved in turbulent atomization. Both liquid and gas temperatures were fixed at a room temperature but the gas pressure was elevated to more than twice the critical pressure of $SF_{6}$. Therefore, the liquid surface was in a thermodynamic state close to a critical mixing condition with suppressed vaporization. Since the surface tension and the surface gas density approach zero and the surface liquid density, respectively, phenomena equivalent to those which would appear when a very high speed laminar flow of water were injected into the atmospheric-pressure air can be observed by issuing $SF_{6}$ liquid at low speeds in micro-gravity environment which avoid disturbances due to gravity forces. The instability ob near-critical mixing surface jet was quantitatively characterized using a newly developed device, which could issue a very small amount of $SF_{6}$ liquid at small constant velocity into a very high-pressure $N_2$ gas.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1359-1361
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• 1996

This paper describes a design of real time fuzzy controller using Minimum fuzzy control Rule Selection Method(MRSM). The control algorithm of dynamic systems needs less computation time and memory. To reduce the computation time of fuzzy logic controller, minimum number of rules are to be selected for the fuzzy input variable. The universe of discourse is divided by the number of linguistic labels to allocate the assigned membership function to the fuzzy input variables. In this case, since fuzzy input variables are continuous, scale factor SU is tuned independently. According to increment of SU control surface is improved to adapt the change of system parameter. At this, crisp control surface is increased. With the increament of crisp control surface, fuzzy control surface is reduced. When error state deviates from desirable error state, crisp control surface is more useful than fuzzy control surface for obtaining fast rising time.

• Proceedings of the Korean Vacuum Society Conference
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• 2002.06a
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• pp.183-184
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• 2002

• Bulletin of the Korean Chemical Society
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• v.11 no.3
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• pp.231-235
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• 1990

The activation energy of dissociative adsorption of oxygen on polycrystalline nickel surface is calculated from adsorption isotherms obtained using X-ray photoelectron spectroscopy. Negative value of this activation energy (-5.9 kJ/mol) indicates that the adsorption takes place through an undissociated precursor state. An adsorption energy for this precursor state is calculated assuming the precursor state as a moleculary physisorbed state ($E_{ad}$ = -7.9 kJ/mol). Finally, an adsorption isotherm equation is derived as a function of the gas exposure, which agrees with the experimental isotherms reasonably good.