• Tribology and Lubricants
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• v.15 no.3
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• pp.248-256
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• 1999

Many tribological components in automobile engine undergo high load and sliding speed with thin film thickness. The lubrication characteristics of the components are regarded as ether hydrodynamic lubrication or boundary lubrication, whereas in a working cycle they actually have both characteristics. Many modem engine lubricants have various additives for better performance which make boundary film formation even under hydrodynamic lubrication regime. Conventional Reynolds equation with the viewpoints of continuum mechanics concerns only bulk viscosity of lubricant, which means that its simulation does not give insights on boundary lubrication characteristics. However, many additives of modern engine lubricant provide mixed modes of boundary lubrication characteristics and hydrodynamic lubrication. Especially, high molecular weight polymeric viscosity index improvers form boundary film on the solid surface and cause non-Newtonian fluid effect of shear thinning. This study has performed the investigation about journal bearing system with the mixed concepts of boundary lubrication and hydrodynamic lubrication which happen concurrently in many engine components under the condition of viscosity index improver added.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.194-197
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• 1997

The LB technique is one of the most powerful fabricating methods of organic ultra-thin film, which deposits a monolayer films in molecular level on the surface of the substrate. We have investigated the electrical characteristics of Myristic acid, Stearic acid and Arachidic acid LB films for horizontal direction to develop for the gas sensor. The optimum conditions for a film deposition were obtained by measurement of $\pi$-A isotherm. The status of the deposited film was confirmed by measurement of UV absorbance. We could distingished the difference of I-V characteristics for the fatty acid for the horizontal direction. The conductivity of fatty acid LB films for horizontal direction was 10$^{-7}$ ~ 10$^{-9}$ [S/cm] that mean like semiconductor.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.71-74
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• 1998

$Er^{3+}$ doped $NdF_{3}$ single crystalline thin films with smooth, microcrack-free, and high-crystalline quality were grown on $CaF_{2}(111)$ substrate at $500^{\circ}C$by molecular beem epitaxy(MBE). The relation-ship between subcell and supercell showing the reconstructed $3^{1/2} \times 3^{1/2}$ structure was studied by reflection high-energy electron diffraction(RHEED) investigation. The film surface and the growth mode were examined in studied by RHEED patterns and atomic force microscope(AFM) images ex situ. The crystallinity of film and the lattice mismatch between $NdF_{3}Er}^{3+}(0002)$ film and $CaF_{2}(111)$ substrate depending in the $Er^{3+}$ concentration were investigated by X-ray rocking curve analysis.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.203-203
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• 2009

We report on the epitaxial growth of tetragonal $DO_{22}$-type Mn3Ga films on GaSb (001) using molecular beam epitaxy and the related structural and magnetic properties. The as-studied $Mn_3Ga$ film was found to exhibit relatively small coercivity around 400 Oe, which differs greatly from the hard magnetic properties of $Mn_3Ga$ bulk specimen or films that are normally reported. This difference was probably attributed to the effects of the GaSb (001) substrate that forced the $Mn_3Ga$ film to be two-dimensionlly stabilized in the (114) orientation and thus led to the modified intrinsic properties of $Mn_3Ga$ films. The growth orientation of the Mn3Ga (114)//GaSb (001) also caused the easy magnetocrystalline direction located in the film plane due to the dominant shape anisotropy in the thin films.

• Macromolecular Research
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• v.10 no.1
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• pp.2-12
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• 2002

The small-angle X-ray scattering (SAXS) beamline BL4C1 at the 2.5 GeV storage ring of the Pohang Accelerator Laboratory (PAL) has been in its first you of operation since August 2000. During this first stage it could meet the basic requirements of the rapidly growing domestic SAXS user community, which has been carrying out measurements mainly on various polymer systems. The X-ray source is a bending magnet which produces white radiation with a critical energy of 5.5 keV. A synthetic double multilayer monochromator selects quasi-monochromatic radiation with a bandwidth of ca. 1.5%. This relatively low degree of monochromatization is sufficient for most SAXS measurements and allows a considerably higher flux at the sample as compared to monochromators using single crystals. Higher harmonics from the monochromator are rejected by reflection from a flat mirror, and a slit system is installed for collimation. A charge-coupled device (CCD) system, two one-dimensional photodiode arrays (PDA) and imaging plates (IP) are available its detectors. The overall performance of the beamline optics and of the detector systems has been checked using various standard samples. While the CCD and PDA detectors are well-suited for diffraction measurements, they give unsatisfactory data from weakly scattering samples, due to their high intrinsic noise. By using the IP system smooth scattering curves could be obtained in a wide dynamic range. In the second stage, stating from August 2001, the beamline will be upgraded with additional slits, focusing optics and gas-filled proportional detectors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.24-26
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• 2002

In this paper, we discuss the electrical properties of self-assembled (2'-amino-4,4-di(ethynylphenyl)-5'-nitro-l-(thioacetyl)benzene), which has been well known as a conducting molecule having possible application to molecular level NDR device. The phenomenon of negative differential resistance (NDR) is characterized by decreasing current through a junction at increasing voltage. also fabrication of MIM-type molecular electronic and the Molecular Level Using Scanning Tunneling Microscopy

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.111-115
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• 2003

Nanoindentation is simply an indentation test in which the length scale of the penetration is measured in nanometres rather than microns or millimetres, the latter being common in conventional hardness tests. Three-dimensional molecular dynamics simulations have been conducted to evaluate the nanoindentation test. Molecular dynamics simulations were carried out on single crystal copper by varying crystal orientations to investigate nano-behavior of material beneath an indenter in nanoindentation. Morse potential function was used as an interatomic force between indenter and thin film. The result of the simulation shows that crystal orientation significantly influenced the slip system, dislocation nucleation and dislocation behavior.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.343-348
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• 2007

Molecular dynamics study of thermal NIL (Nano Imprint Lithography) process is performed to examine stamp-resist interactions. A layered structure consists of Ni stamp, poly-(methylmethacrylate) thin film resist and Si substrate was constructed for isothermal ensemble simulations. Imposing confined periodicity to the layered unit-cell, sequential movement of stamp followed by NVT simulation was implemented in accordance with the real NIL process. Both vdW and electrostatic potentials were considered in all non-bond interactions and resultant interaction energy between stamp and PMMA resist was monitored during stamping and releasing procedures. As a result, the stamp-resist interaction energy shows repulsive and adhesive characteristics in indentation and release respectively and irregular atomic concentration near the patterned layer were observed. Also, the spring back and rearrangement of PMMA molecules were analyzed in releasing process.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.651-654
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• 2002

We carried out 2-dimensional numerical calculations of electrostatic potential for triode field emitters with planar cathodes using the finite element method. As it turned out, the conventional triode structure with a planar cathode suffered from large gate current and wide spreading of emitted electrons. To circumvent these shortcomings, we proposed a new triode structure. By simply inserting a conducting layer of proper thickness on top of the cathode layer, we were able to modify the electric field distribution on the cathode surface so that low gate current and electron-focusing effect were achieved, simultaneously.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1572-1574
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• 2002

In this paper, we discuss the electrical properties of self-assembled (2'-amino-4,4-di(ethynylp henyl)-5'-nitro-1-(thioacetyl)benzene), which has been well known as a conducting molecule having possible application to molecular level NDR device. The phenomenon of negative differential resi(NDR) is characterized by decreasing current th a junction at increasing voltage, also fabricatio MIM-type molecular electronic device and the Molecular Level Using Scanning Tunneling Microscopy.