• Journal of the Korean Society for Heat Treatment
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• v.13 no.4
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• pp.224-230
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• 2000

Garbon steel(SM35C) was gas nitrocarburized at $580^{\circ}C$ in $55%N_2-40%NH_3-5%CO_2$ mixed gas atmosphere, and then the steel was induction hardened at $850^{\circ}C$. The microstructure of gas nitrocarburized surface layer was observed by optical microscope and SEM. The phase analysis was carried out by X-ray diffraction method. The mechanical properties of gas nitrocarburized SM35C steel was evaluated by hardness, wear and fatigue test. The thickness of compound and diffusion layer were increased with increasing the gas nitrocarburizing time and the densest compound layer was obtained at 3 hours gas nitrocarburizing time. In case of 15sec induction hardening after gas nitrocarburizing, the surface hardness was decreased from 800Hv to 630Hv owing to the decomposition of compound layer, but wear resistance was increased because of increased hardness of diffusion layer. The fatigue strength of induction hardened steel after gas nitrocarburizing, $58kgf/mm^2$, was higher than $41.5kg/mm^2$ of gas nitrocarburized steel and $45kg/mm^2$ of induction hardened steel, respectively.

• 기술발표회
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• s.2006
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• pp.320-328
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• 2006

In this test, there was two dimensional model loading test implemented for analysis with respect to the problem of evaluating bearing capacity and the application range on the dredged and reclaimed ground. It was got following conclusion through comparison of button's and Brown&Meyerhof"s equation with experimental result that was obtained by 2 dimensions model loading test. For the difference between average undrained shear strength by 2/3B of loading board width and under 2/3B is more than ${\pm}$ 50%, application of Nc(coefficient of bearing capacity was used in that case $\phi$=0 analysis is considered in the single layer) was declined. Brown&Meyerhof(1969)'s equation was underestimated comparing with loading test result, while Button(1953)'s equation was overestimated comparing with loading test result applied dividing as double layers of upper dessication layer and lower soft layer about dredged and reclaimed ground. Also, bearing capacity factors, Nc that was calculated by using button's equation was estimated greatly about 1.7 times more than bearing capacity factors, Nc that was calculated by using Brown&Meyerhof's equation. Bearing capacity factors, Nc that was calcuated by using Brown&Meyerhof's and Button's equation was evaluated each 2.3-3.6 times, 1.3-2.1 times smaller than bearing capacity factors, Nc5.14 that was calcuated by using Meyerhof's equation in case of unit layer.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2420-2424
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• 2009

We have successfully demonstrated of metal-insulator-semiconductor (MIS) capacitors with $Al_2O_3/p-Si$ structures. The $Al_2O_3$ film was grown at $200^{\circ}C$ on H-terminated Si wafer by atomic layer deposition (ALD) system. Trimethylaluminum [$Al(CH_3)_3$, TMA] and $H_2O$ were used as the aluminum and oxygen sources. A cycle of the deposition process consisted of 0.1 s of TMA pulse, 10 s of $N_2$ purge, 0.1 s of $H_2O$ pulse, and 60 s of $N_2$ purge. The 5 nm thick $Al_2O_3$ layer prepared on Si substrate by ALD exhibited excellent electrical properties, including low leakage currents, no mobile charges, and a good interface with Si.

• Korean Journal of Environmental Biology
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• v.24 no.1 s.61
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• pp.67-80
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• 2006

The effect of environmental forcing on picophytoplankton distribution pattern was investigated in the tropical and subtropical western Pacific (TSWP) and the East Sea in September, 2002, and the continental shelf of the East China Sea (C-ECS) in August, 2003. The abundance of picophytoplankton populations, Synechococcus, Prochlorococcus and picoeukaryotes were determined by flow cytometry analyses. Picophytoplankton vertical profiles and integrated abundance $(0\sim100\;m)$ were compared with these three physiochemically different regions. Variation patterns of integrated cell abundance of Synechococcus and Prochlorococcus in these three regions showed contrasting results. Synechococcus showed average abundance of $84.5X10^{10}\;cells\;m^{-2}$, in the TSWP, $305.6X10^{10}\;cells\;m^{-2}$ in the C-ECS, and $125.4X10^{10}\;cells\; m^{-2}$ in the East Sea where increasing cell concentrations were observed in the region with abundant nutrient. On the other hand, Prochlorococcus showed average abundance of $504.5X10^{10}\;cells\;m^{-2}$ in the TSWP, $33.2x10^{10}\;cells\;m^{-2}$ in the C-ECS, and $130.2X10^{10}\;cells\;m^{-2}$ in the East Sea exhibiting a distinctive pattern of increasing cell abundance in oligotrophic warm water. Although picoeukaryotes showed a similar pattern to Synechococcus, the abundance was 1/10 of Synechococcus. Synechococcus and picoeukaryotes showed ubiquitous distribution whereas Prochlorococcus generally did not appear in the C-ECS and the East Sea with low salinity environment. The average depth profiles for Synechococcus and Prochlorococcus displayed uniform abundance in the surface mixed layer with a rapid decrease below the surface mixed layer. for Prochlorococcus, a similar rapid decreasing trend was not observed below the surface mixed layer of the TSWP, but Prochlorococcus continued to show high cell abundance even down to 100 m depth. Picoeukaryotes showed uniform abundance along $0\sim100\;m$ depth in the C-ECS, and abundance maximum layer appeared in the East Sea at $20\sim30\;m$ depth.

• Progress in Superconductivity and Cryogenics
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• v.8 no.4
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• pp.8-11
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• 2006

High temperature superconducting coated conductor has various buffer structures on Ni-W alloy. We comparatively studied the growth conditions of a multi buffer layer $(CeO_2/YSZ/CeO_2)$ and a single buffer layer$(CeO_2)$ on textured Ni-W alloy tapes. XRD data showed that the qualities of in-plane and out-of-plane textures of the two type buffer structures were good. Also, we investigated the properties of SmBCO superconducting layer that was deposited on the two type buffer structure. The SmBCO superconducting properties on the single and multi buffer structure showed different critical current values and surface morphologies. FWHM of In-plane and out-of-plane textures were $7.4^{\circ},\;5.0^{\circ}$ in the top CeO2 layer of the multi-buffer layers of $CeO_2/YSZ/CeO_2$, and $7.3^{\circ},\;5.1^{\circ}$ in the $CeO_2$ single buffer layer. $1{\mu}m-thick$ SmBCO superconducting layers were deposited on two type buffer layer. $I_c$ of SmBCO deposited on single and multi buffer were 90 A/cm, 150 A/cm and corresponding $J_c$ were $0.9MA/cm^2,\;1.5MA/cm^2$ at 77K in self-field, respectively.

• Progress in Superconductivity
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• v.7 no.2
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• pp.120-129
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• 2006

We comparatively studied the epitaxial growth conditions of $CeO_2$ and $Y_2O_3$ thin buffers on textured Ni tapes using rf magnetron sputtering and investigated the feasibility of getting a single mixture layer or sequential layers of $CeO_2$ and $Y_2O_3$ for more simplified buffer architecture. All the buffer layers were first deposited using the reducing gas of $Ar/4%H_2$ and subsequently the reactive gas mixture of Ar and $O_2$, The crystalline quality and biaxial alignment of the films were investigated using X-ray diffraction techniques (${\Theta}-2{\Theta},\;{\phi}\;and\;{\omega}\;scans$, pole figures). The $CeO_2$ single layer exhibited well developed (200) epitaxial growth at the condition of $10%\;O_2$ below an $450^{\circ}C$, but the epitaxial property was decreased with increasing the layer thickness. $Y_2O_3$ seldom showed optimum condition for (400) epitaxial growth. The sequential architecture of $CeO_2/Y_2O_3/CeO_2$ having good epitaxial property was achieved by sputtering at a temperature of $700^{\circ}C$ on the initial $CeO_2$ bottom layer sputtered at $400^{\circ}C$. Cracking of the sputtered buffer layers was seldom observed except the double layer structure of $CeO_2/Y_2O_3$.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.41-41
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• 1998

Rare earth metal films have been used as a buffer layer for growing ferroelectric t thin film or a seed layer for magnetic multilayer. But when it was deposited on s semiconductor substrates for the application of magneto-optic (MO) storage media, it i is difficult to exactly measure magnetic cons떠nts due to shunting current, and so it n needs to grow metal films on insulator substrate to reduce such effect. Recently, it w was reported that ultra-thin Pt layer were epitaxially grown on A12O:J by ion beam s sputtering in 비떠 high vacuum and it can be used as a seed layer for the growth of C Co-contained magnetic multilayer. In this stu$\phi$, Pt thin film were epi떠xially grown on AI2D3 ($\alpha$)OJ) by RF magnetron s sputtering. The crystalline structure was analyzed by transmission electron microscope ( (TEM) and Rutherford Back Scattering (RBS)/Ion Channeling. In TEM study, Pt was b believed to be twinned on AI잉3($\alpha$)01) su$\pi$ace about Pt(ll1) plane.Moreover, RBS c channeling spectra showed that minimum scattering yield of Pt(111)/AI2O:J(1$\alpha$)OJ) was 4 4% and Pt(11J)/AI2D3($\alpha$)OJ) had 3-fold symmetry.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.218-223
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• 2012

Fe-(8.5, 18.5, 28.3, 36.9) wt% Cr alloys were corroded between 600 and $800^{\circ}C$ for up to 70 h in a 1 atm gas mixture that consisted of 0.0242 atm of $H_2S$, 0.031 atm of water vapor, and 0.9448 atm of nitrogen gas. Their corrosion resistance increased with an increment in the Cr content. The Fe-8.5%Cr alloy corroded fast, forming thick, fragile, nonadherent scales that consisted primarily of an outer FeS layer and an inner (Fe, Cr, O, S)-mixed layer. The outer FeS layer grew into the air by the outward diffusion of $Fe^{2+}$ ions, whereas the inner mixed layer grew by the inward diffusion of oxygen and sulfur ions. At the interface of the outer and inner scales, voids developed and cracking occurred. The Fe-(18.5, 28.3, 36.9)% Cr alloys displayed much better corrosion resistance than the Fe-8.5Cr alloy, because thin $Cr_2O_3$ or $Cr_2S_3$ scales formed.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.155-162
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• 2012

The Thomsen-Haskell method was used to determine sensitivities of the Rayleigh-wave phase velocities and spectral amplitude of vertical ground motion to insertion of a single velocity-anomaly layer into overburden underlain by a basement. The reference model comprised a 9-m thick overburden with shear-wave velocity (${\nu}_s$ of 300 m/s above a half-space with ${\nu}_s$ = 1000 m/s. The inserted layer, with a velocity of 150, 225, 375, or 450 m/s and a thickness of 1, 2, or 3 m, was placed at depths increasing from the surface in increments of 1 m. Phase velocities were computed for frequencies of 4 to 30 Hz. For inserted layer models, we placed an anomalous layer with thickness of 1 ~ 3 m, shear-wave velocity of 150 ~ 450 m/s, and at depths of 0 ~ 8 m in the overburden. The frequency range of 8 ~ 20 Hz were the most sensitive to the difference of $C_R$ between the inserted and reference models (${\Delta}C_R$) for h = 1 m and the frequency range got wide as h increased. For all of the models, the spectral amplitudes of the fundamental mode exceeded those of the $1^{st}$-higher mode except at frequencies just above the low-frequency cutoff of the $1^{st}$-higher mode.

• Bulletin of the Korean Chemical Society
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• v.14 no.2
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• pp.244-250
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• 1993

The interaction of 1,3,5-trithian molecule with Ag(111) surface is studied employing Extended Huckel method. The Ag(111) surface is modeled by the three layer metal clusters composed of 43 Ag atoms. We assume that the 1,3,5-trithian is lying flat on Ag(111) surface in the chair conformation. The geometry of 1,3,5-trithian itself is assumed to be the same as in the gas phase, which is obtained through the AM1 SCF-MO calculation with full geometry optimization. The calculation for 3-fold site adsorption leads to the weakening of C-S bond, which is compatible with the observed 5 cm$^{-1}$ decrease of the C-S stretching frequency upon surface adsorption, while the on-top site adsorption leads to strengthening of C-S bond. The major component of the C-S bond of trithian is S $3p_{pi}\;(S\;3p_x+S\;3p_y)$ and therefore only the 3-fold site adsorption causes the weakening of this bond. In addition, it is found that the trithian molecule binds to the 3-fold site more strongly.