• 한국초전도ㆍ저온공학회논문지
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• 제8권3호
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• pp.18-22
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• 2006

We obtained in-situ $MgB_2$ thin films in an one-step process using ESSD (Evaporation Sputtering Simultaneous Deposition) method. In our approach. the Ma evaporator is designed specially Mg and B are simultaneously evaporated and sputtered, respectively, in the specially designed ESSD chamber. The background pressure was less than $1{\times}10^{-6}$ Torr. The substrate temperature was kept at 623 K. The film properties were investigated by both electrical resistivity and PPMS. As a result, typical $T_c$ of films was 11 K.

• 대한화학회지
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• 제56권4호
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• pp.448-458
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• 2012

In order to develop alloy resistance in aggressive sulphat ion, the corrosion behavior of metallic glasses $Ni_{92{\cdot}3}Si_{4.5}B_{32}$, $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ (at %) at different concentrations of $H_2SO_4$ solutions was examined by electrochemical methods and Scanning Electron Microscope (SEM) and X-ray Photoelectron Microscopy (XPS) analyses. The corrosion kinetics and passivation behavior was studied. A direct proportion was observed between the corrosion rate and acid concentration in the case of $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ alloys. Critical concentration was observed in the case of $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ alloy. The influence of the alloying element is reflected in the increasing resistance of the protective film. XPS analysis confirms that the protection film on the $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ alloy was NiS which is less protective than that formed on Cr containing alloys. The corrosion rate of $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$. alloys containing 7% and 13% Cr are $7.90-26.1{\times}10^{-3}$ mm/y which is lower about 43-54 times of the alloy $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ (free of Cr). The high resistance of $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ alloy at the very aggressive media may due to thicker passive film of $Cr_2O_3$ which hydrated to hydrated chromium oxyhydroxide.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1380-1387
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• 2000

The existing theoretical models for steady two-dimensional free convective laminar film condensation of pure saturated or superheated vapor under atmospheric pressure on isothermal vertical wall have been reviewed. To investigate the effects such as inertia, thermal convective and liquid-vapor interface shear stress, the models of constant or variable properties in liquid film for condensation of saturated vapor are compared in detail with Nusselt model. Also, for condensation of superheated vapor, the effects of superheated temperature and variable properties in liquid and vapor layers are examined and then a new correlation is proposed to predict the heat transfer. The results are in good agreement with the Shang's correlation within 2% errors.

• 대한기계학회논문집B
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• 제25권7호
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• pp.975-980
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• 2001

The thermal analysis of the hot roller in a dry film laminator is studied numerically by steady-state two-dimensional heat transfer. In the laminating process for PDP glass or PCB, the temperature distributions in a hot roller are presented considering the effects of the roller rotation speed and the inner and outer radii of the roller. The results show that the temperature distributions are strongly dependent on Peclet number. If Pe number becomes larger, the iso-thermal lines are more concentric about the rotating axis and the temperature difference on the hot roller surface decreases exponentially. It also shows that if the contact angle between the roller and the film becomes smaller the temperature difference becomes smaller. However, the changes of the rollers inner or outer radius have little effect on the temperature difference.

• Rapid Communication in Photoscience
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• 제2권1호
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• pp.24-27
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• 2013

A polymeric photobase generator containing oxime-urethane groups is applied to a fluorescence micropatterning material. Polymer bearing oxime-urethane groups was prepared by copolymerization of methyl methacrylate with methacryloyloxyethyl benzophenoneoxime urethane (MBU). The reaction of amino groups in the irradiated copolymer film with dansyl chloride (Dns-Cl) was monitored by using UV absorption, IR absorption and fluorescence spectroscopy. The fluorescence spectrum of the Dns-Cl-treated irradiated copolymer film shows a strong fluorescence with a fluorescence maximum wavelength at 510 nm. A blue fluorescent micropattern with a line width of $2{\sim}3{\mu}m$ was obtained. Treatment of the irradiated copolymer film with Dns-Cl and rhodamine B mixture led to the formation of green, red, and orange-colored fluorescence micropatterns. Thus, various colored micropatterns on a single polymer film can be obtained by selective excitation of each dye molecules.

• 한국산업정보학회논문지
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• 제6권1호
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• pp.70-76
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• 2001

NdFeB로 만들어진 permanent magnet dc driver는 많은 분야에서 사용된다. 그중 소형 disk type servo driver는 컴퓨터의 hard disk driver나 floppy driver등과 같은 소형기기의 구동용으로 사용된다. 기존의 dc drive는 coil를 감아 winding으로 사용한다. 만들어진 driver에는 coper printed multilayer winding을 사용하였다. 이 논문에서는 thin film multilayer winding의 제조방법, 특성에 관하여 논한다. 또한 dc driver의 commutation를 위해 사용되는 hallsensor 대신에 비 선형 특성의 MR sensor를 선형화시켜 driver의 commutation에 사용하였으며 이렇게 만들어진 소형 driver의 rpm, torque등의 특성을 연구하였다.

• Journal of Magnetics
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• 제12권1호
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• pp.27-30
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• 2007

Experimental evidence suggests that spin pinning conditions for standing spin mode in polycrystalline $Ni_{84}Fe_{16}$ alloy film, is confirmed using the four categories of Camley et al. and the value of q$\bot$ for the pinning conditions, this was achieved by performing Brillouin light scattering measurements. The value of q$\bot$ was observed, in order to increase at a rate of $\pi$/2 with an increasing mode number. With this condition, the coexistence of standing spin wave modes was shown, with intermediate pinning, in addition to free and strong pinning. The values for spin-wave-stiffness constant ($D_B$), g-factor (g), and surface magnetization (4$\pi$M) of the Permalloy film were obtained from the results of BLS, and determined to be $D_B=1.85{\pm}0.05Oecm^2$, $g=2.11{\pm}0.02$, and 4$\pi$M=8.7 kG, respectively.

• 대한기계학회논문집B
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• 제23권3호
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• pp.419-430
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• 1999

Measurements of local blowing ratio and ammonia-diazo flow visualizations have been conducted for a shower-head film cooling on a first-stage turbine stator. In this study, six rows of normal holes are drilled symmetrically on the semicircular leading edge of a simulated blunt body. The measurements show that for an average blowing ratio based on freestream velocity, M, of 0.5, local average mass flow rate through the first two rows of the holes is less than those through the second and third two rows of the holes, and the fraction of mass flow rate through the first two rows to total mass flow rate has a tendency to increase with the increment of M. The flow visualizations reveal that the injection through the first two row results in inferior film coverage even In the case of M = 0.5, meanwhile the row of holes situated at farther downstream location provides higher film-cooling performances for all tested M. This is because film-cooling effectiveness depends on local mainflow velocity at the hole location as well as the mass flow rate through each row.

• 대한기계학회논문집B
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• 제28권3호
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• pp.304-314
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• 2004

An experimental study has been conducted to measure the temperature fields and the local film cooling effectiveness for two and three staggered rows of the rectangular shaped-holes with various blowing rates. The hydraulic diameter of rectangular-shaped hole is 10mm. To compare with the film cooling performance of rectangular-shaped hole, two kinds of circular holes are tested. One has the same hydraulic diameter as the rectangular hole and the other has the same cross sectional area. Also, rectangular holes with expanded exit with same inlet area as rectangular ones are tested. Temperature fields are measured using a thermocouple rake attached on three-axis traversing system. Adiabatic film cooling effectiveness on the surface are obtained based on experimental results of thermochromic liquid crystals. The film cooling effectiveness is measured for various blowing rates and compared with the results for the cylindrical holes. In case of 2 rows, the rectangular holes has better performance than circular holes due to its slot-like geometry. In case of 3 rows, the effecta of hole shape is not clear.

• 대한기계학회논문집B
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• 제26권7호
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• pp.927-936
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• 2002

An experimental study has been conducted to investigate the heat/mass transfer characteristics within a film cooling hole of square cross-section for various blowing ratios and Reynolds numbers. The experiments have been performed using a naphthalene sublimation method and the flow field has been analyzed by numerical calculation using a commercial code. A duct flow enters into a film cooling hole in a cross-direction. For the film cooling hole with square cross-section, it is observed that the reattachment of separated flow and the vortices within the hole enhance considerably the heat/mass transfer around the hole entrance region. The heat/mass transfer on the leading edge side of hole exit region increases as the blowing ratios decrease because the main flow induces a secondary vortex. Heat/mass transfer patterns within the square film cooling hole are changed little with the various Reynolds numbers.