• Proceedings of the KSME Conference
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• 2007.05a
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• pp.210-214
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• 2007

Silicon nanoparticles are widely studied as a material with great potential for wide applications. For application to present industry, it should be easy to control the characteristics of nanoparticle including the size and structure. In this paper, we investigated the formation of Si nanoparticle using pulse plasma technology. Plasma technology is already quite common in device industry and the size of nanoparticle can be easily controlled according to plasma pulse duration. An inductively-coupled plasma chamber with RF power (13.56 MHz) was used with DC-biased grid $(-200\sim+200\;V)$ installed above the substrate. In order to measure the shape and size of nanoparticle, TEM was used. It was found that the size of nanoparticles can be controlled well with the plasma pulse duration and the collection efficiency is increased with the use of either negative or positive DC-bias.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.5
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• pp.93-99
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• 1998

The chirping characteristics of InGaAsP electroabsorption modulatiors have been analyzed. The effective .alpha. parameters for large signal modulation were estimated by comparing the pulse shape after fiber transmission with constant chirping assumption.We investigated the structure and the operating condition of the modulator to improve the chirping characteristics. The .alpha. parameters were calculated as the function of wavelength detuning and the bias voltage. To minimize the chirping performance, high bias voltage and a small wavelength detuning and the bias voltage. To minimize the chirping performance, high bias voltage and a small wavelength detuning were preferred. An negative .alpha. value is achieved at the wavelength detuning below 30meV with a proper bias voltage so that pulse compression effect was expected.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.224-229
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• 2013

Vanadium oxide thin films were deposited on $c-Al_2O_3$ (001) substrate by in-situ RF magnetron sputtering. Oxygen partial pressure was adjusted to prepare thermochromic $VO_2$ phase. X-ray diffraction patterns and scanning electron microscopy convincingly showed that plate-like $V_2O_5$ grains were changed into round-shape $VO_2$ grains as oxygen partial pressure decreased. After the optimized deposition conditions were fixed, the effect of substrate temperature and orientation on the optical properties of $VO_2$ thin films was analyzed.

• Progress in Superconductivity and Cryogenics
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• v.15 no.3
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• pp.20-23
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• 2013

In the development of high temperature superconducting (HTS) power machines, HTS bushing is one of core technologies. In particular, the insulation body with sheds and electrical insulation at cryogenic temperature have attracted a great deal of interest from the view point of the size, weight and efficiency of bushing. In this study, the electrical and mechanical characteristics of various insulators for body in liquid nitrogen ($LN_2$) were investigated. And the surface discharge distance, collar length of GFRP sheds were studied. To emit bubbles between sheds, the shape and arrangement of shed were studied. The shed structure for 60 kV class HTS bushing were designed with regular arrangement.

• Journal of Korean Association for Spatial Structures
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• v.2 no.3 s.5
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• pp.103-113
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• 2002

This thesis investigates vibration response characteristics of building frames in which dampers are installed. The frames belong to passively vibration-controlled. Structures which utilizes energy dissipation of mechanical dampers provided in the structure. In this thesis, a turbulent flow damper sealed by visco-elastic material was dealt with as the device of passive vibration control. To investigate the resisting force characteristics of the damper, harmonic vibratration tests were carried out. Based on the test results, a theoretical model of the damper resistance was presented and a method of identifying the model parameters was proposed. Shaking table tests of the frame with and without the dampers were carried out and the effectiveness of the damper was examined. The response of the frame with the dampers was reduced to 1/2 or 1/3 of the cases without the damper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.934-937
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• 2001

It is well-known that the micro fabrication technology of micro parts are the high energy beam or silicon-based micro machining method such as LIGA Process, Laser machining, photolithography and etching technology. But, for fabricating complex 3-D structure it is better to use mechanical machining. This machining method by the mechanical machine tool with nanometer accuracy is getting attention in some field-especially micro optics machining such as grating, holographic lens, micro lens array, fresnel lens, encoder disk etc.. In this study, we survey the micro fabrication by mechanical cutting method and set up the mechanical micro machining system. And we carried out micro cutting experiments for micro parts with v-shape groove.

• Journal of Magnetics
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• v.2 no.4
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• pp.116-122
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• 1997

To determine whether there is an ionic substitution of Ni, Co, Mn, and Al for Fe in synthetic goethites these materials have been studied by M$\ddot{o}$ssbauer spectroscopy at various temperatures ranging from 77 to 400 K. It is found that the presence of substituting elements in magnetically ordered structure of crystals may change the shape of M$\ddot{o}$ssbauer spectra of these caterials. The approximate distribution function of the effective magnetic field in the Fe nucleus p(Hn) is obtained from the M$\ddot{o}$ssbauer spectra. It is noted that the mean value of p(Hn) and its integral width can be taken as a measure of substitution in goethites.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.2
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• pp.228-235
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• 2004

In this thesis, it is designed efficient electrode formation on the organic luminescent device. ITO electrode is treated with $O_2$plasma. In order to inject hole efficiently, there is proposed the shape of anode that inserted plasma polymerized films as buffer layer between anode and organic layer using thiophene monomer. It is realized efficiently electron injection to aluminum due to introduce the quantum well in cathode. In the case of device inserted the buffer layer by using the plasma poiymerization after $O_2$plasma processing for ITO transparent electrode, since it forms the stable interface and reduce the moving speed of hole, the recombination of hole and electronic ate made in the omitting layer. Compared with the devices without buffer layer, the turn-on voltage was lowered by 1.0(V) doc to the introduction of buffer layer Since the quantum well structure is formed in front of cathode to optimize the tunneling effect, there is improved the power efficiency more than two times.

• 보존과학연구
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• s.19
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• pp.61-74
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• 1998

Conservation Treatment Process 1. Inlaying is observed at the back and head of a sword to grasp the inner structure of relics by photographing X-ray. 2. After removing rust of surface, inlaying emerge. 3. After hardening, inlaying emerge to magnetite layer by standing Scapel and Vibrotool throught microscope. Charcterization 1. Most of domestic inlaying become designed to the head of a sword but this inlaying become designed to gold inlaying to the back of a sword. 2. Inlaying is the technique to groove V-shape on the surface of relice and to put gold thread in.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1334-1340
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• 2017

In this paper, a tie-plate shape is optimized by using the numerical technique to reduce the stray load loss of the tie-plate which is a mechanical structure for assembling and supporting of the transformer core. The eddy current loss of the structure is calculated by an electromagnetic field FEM program and the results are compared with 4 different shapes of tie-plates. Since the thickness of the tie-plate is very thin, and the skin depth is very small, the number of FE elements for 3-D transformer model is too big to solve. So, the surface impedance boundary condition (SIBC) is used to reduce the system matrix size and its computing time. To verify the method a 2.5 MVA 22,900/380V distribution transformer is simulated using one objective function and three design variables with some constraints. The final optimized tie-plate has three slots of 6 mm width and 23 mm gap, and the loss is reduced by 75 %. Consequently, the proposed algorithm seems to be considerably applicable to electric machinery as well as power transformer.