• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.212-212
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• 2013

We fabricate and characterize top gate Graphene transistor using aluminum oxide as a gate insulator by atomic layer deposition (ALD). It is found that due to absence of functional group and dangling bonds, ALD of metal oxide is difficult on Graphene. Here we used 4-mercaptopheneol as a functionalization layer on Graphene to facilitate uniform oxide coverage. Contact angle measurement and Atomic force microscopy were used to confirm uniform oxide coverage on Graphene. Raman spectroscopy revealed that functionalization with 4-mercaptopheneol does not induce any defect peak on Graphene. Our device shows mobility values of 4,000 $cm^2/Vs$ at room temperature which also suggest top gate stack does not significantly increase scattering. The noncovalent functionalization method is non-destructive and can be used to grow ultra-thin dielectric for future Graphene applications.

• Korean Journal of Materials Research
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• v.32 no.4
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• pp.200-209
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• 2022

In this study, defects generated in the YSZ coating layer of the IN738LC turbine blade are investigated using an optical microscope and SEM/EDS. The blade YSZ coating layer is composed of a Y-Zr component top coat layer and a Co component bond coat layer. A large amount of Cr/Ni component that diffused from the base is also measured in the bond coat. The blade hot corrosion is concentrated on the surface of the concave part, accompanied by separation of the coating layer due to the concentration of combustion gas collisions here. In the top coating layer of the blade, cracks occur in the vertical and horizontal directions, along with pits in the top coating layer. Combustion gas components such as Na and S are contained inside the pits and cracks, so it is considered that the pits/cracks are caused by the corrosion of the combustion gases. Also, a thermally grown oxide (TGO) layer of several ㎛ thick composed of Al oxide is observed between the top coat and the bond coat, and a similar inner TGO with a thickness of several ㎛ is also observed between the bond coat and the matrix. A PFZ (precipitate free zone) deficient in γ' (Ni₃Al) forms as a band around the TGO, in which the Al component is integrated. Although TGO can resist high temperature corrosion of the top coat, it should also be considered that if its shape is irregular and contains pore defects, it may degrade the blade high temperature creep properties. Compositional and microstructural analysis results for high-temperature corrosion and TGO defects in the blade coating layer used at high temperatures are expected to be applied to sound YSZ coating and blade design technology.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.345-346
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• 2008

We have studied an emission spectra of top-emssion organic light-emitting diodes(TEOLED) due to a change of cathode and organic layer thickness. Device structure is Al(100nm)/TPD(xnm)/$Alq_3$(ynm)/LiF(0.5nm)/cathode. And two different types of cathode were used; one is LiF(0.5nm)/Al(25nm) and the other is LiF(0.5nm)/Al(2nm)/Ag(30nm). While a thickness of hole-transport layer of TPD was varied from 35 to 65nm, an emissive layer thickness of $Alq_3$ was varied from 50 to 100nm for two devices. A ratio of those two layer was kept to be about 2:3. Al and Al/Ag double layer cathode devices show that the emission spectra were changed from 490nm to 560nm and from 490nm to 560nm, respectively, when the total organic layer increase. Full width at half maximum was changed from 67nm to 49nm and from 90nm to 35nm as the organic layer thickness increases. All devices show that view angle dependent emission spectra show a blue shift. Blue shift is strong when the organic layer thickness is more than 140nm. Devece with Al/Ag double layer cathode is more vivid.

• The Korean Journal of Ecology
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• v.14 no.2
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• pp.159-169
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• 1991

Floristic cmposition and soil properties were analyzed in chines cork oak(quercus variabilis)cmmunities in the limestone area, tanyang, ch'ungbuk province in korea. The tree layer was composed of quercus dentata, platycarya strobilacea, fraxinus rhynchophylla and others as wel as quercus variabilis. the shrub layer was dominated by ulmus davidiana for. suberosa,shrubby q. variabilis. euonymus alatus and rhus chinensis. among these, u. davidiana for. suberosa was known to have a restricted distribution to calcareous area, and 9 species in the shrub layer including e. alatus, indigofera kirilowii and rhamnus davurica belonged to the calcicole. The herb layer was dominated by carex lanceolata and spodiopogen cotulifer. ten specirs including g. lanceolata, clematis mandshurica, isachne globosa, lithospermum arvense and scabiosa mansenensis belonged to the calcicode. soil texture was classified to clay loam in both top and subsoil. Water cotent and organic matter were consistentl higher in top soil than in subsoil. soil ph rangd 7.8~8.4. Total n concentration in top soil ranged from 0.2 to 0.4mg/g, which was higher than that in subsoil. Available p and exchangeable k concentretion were also significantly higher in op soil than in subsoil. However, exchangeable ca concentration was similar betweenthe top and the subsoil. Unlike the other nutrients, exchangeable mg concentration in top soil was lower than that in subsoil. orangic matter, n, p and k content in this chinese cork oak stand showed as much as the other noncalcareous sites. Soil properties in this study area seemed to have been influenced by casts forming activities of earthworms.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.5
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• pp.673-681
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• 2014

In this paper, a novel low specific on-resistance SOI LDMOS Device with P+P-top layer in the drift region is proposed and investigated using a two dimensional device simulator, MEDICI. The structure is characterized by a heavily-doped $P^+$ region which is connected to the P-top layer in the drift region. The $P^+$ region can modulates the surface electric field profile, increases the drift doping concentration and reduces the sensitivity of the breakdown voltage on the geometry parameters. Compared to the conventional D-RESURF device, a 25.8% decrease in specific on-resistance and a 48.2% increase in figure of merit can be obtained in the novel device. Furthermore, the novel $P^+P$-top device also present cost efficiency due to the fact that the $P^+$ region can be fabricated together with the P-type body contact region without any additional mask.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.209-213
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• 2005

Slow sand filtration processes amended with 5 and 10cm GAC layers at top was compared to same process at bottom in a pilot study for humic substances removal. In case of 5cm GAC layer, the process amended at bottom was superior to the process at top in DOC and UV254nm removal and same trends were observed in case of 10cm GAC layer. Head loss developments of the process GAC at bottom were higher than the process GAC at top so that maintenance of the process GAC at top is easier than the process GAC at bottom.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.4
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• pp.68-74
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• 2002

The FD process is analogous to the direct piston extrusion process where the cold feed filament acts as a piston extruding the molten filament from the heated liquefier through a nozzle. The extruded filament is deposited on top of futureless platform, where the liquefier and the nozzle move in X and Y direction control by computer based on the part geometry. After the first layer, the Z platform indexes down and the next layer get deposited on top of the first layer. the layer by layer building process introduces surface problem. This paper describes effect of slice interval of the parts built by fused deposition modelling rapid prototyping system.

• New & Renewable Energy
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• v.3 no.1 s.9
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• pp.75-82
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• 2007

Aluminum was used as metallic bipolar plate material to reduce a stack weight. The functional materials such as conductive material, Au and nonconductive material, PTFE [polytetrafluoroethylene] were coated on the bipolar plate to enhance electrical contact and corrosion prevention in PEMFC. The active area of bipolar plate is divided into the top layer part that electric current mainly passes, and the bottom layer part that gas and water pass. The bottom layer part in the flow channel needs not to have electrical conductivity because it doesn't pass electric current directly. In this reason, Au on the top layer and PTFE on the bottom layer were coated to apply high electrical conductivity and/or good corrosion resistance. Although the single cell performance using Au-PTFE/Al bipolar plate was shown 78% in comparison with that of graphite, specific power of Au-PTFE/Al bipolar plate(0.4 W/g) was twice as much as graphite bipolar plate.

• ETRI Journal
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• v.44 no.1
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• pp.147-154
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• 2022

We demonstrate a new double-layer structure for stretchable interconnects, where the top surface of a serpentine polyimide support is coated with a thin eutectic gallium-indium liquid metal layer. Because the liquid metal layer is constantly fixed on the solid serpentine body in this liquid-on-solid structure, the overall stretching is accomplished by widening the solid frame itself, with little variation in the total length and cross-sectional area of the current path. Therefore, we can achieve both invariant resistance and infinite fatigue life by combining the stretchable configuration of the underlying body with the freely deformable nature of the top liquid conductor. Further, we fabricated various types of double-layer interconnects as narrow as 10 ㎛ using the roll-painting and lift-off patterning technique based on conventional photolithography and quantitatively validated their beneficial properties. The new interconnecting structure is expected to be widely used in applications requiring high-performance and high-density stretchable circuits owing to its superior reliability and capability to be monolithically integrated with thin-film devices.

• Korean Journal of Heritage: History & Science
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• v.45 no.2
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• pp.72-99
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• 2012

Cheomseongdae, Korea's so-called "star-gazing tower" located in the former Silla Dynasty capital of Gyeongju, is generally believed to have maintained its original shape since its construction in 647. The stone structure was closely examined and measured by Gyeongju National Museum in 1962 and reexamined by Korean National Research Institute of Cultural Heritage in 2009. This research noted the following structural anomalies of Cheomseongdae. A corner of the top rectangle layer was broken diagonally in a form that can never be attributed to a natural cause. The four metal clamps under the top rectangle layer had been missing. Four grooves, with unknown usage, exist on the sides of the long rectangular stones projected out of the circular body at the second and third circular layers from the top. On the second circular layer from the top, there are three flat stones, less than a half as tall as their surrounding stones. The average height of the third circular layer from the top is only 23.5 cm, while the overall average of the entire 27 circular layers is 29.9cm. This research postulates that all these anomalies are due to prior destructions and improper restorations of the structure. The first destruction and restoration of Cheomsengdae was likely to have occurred before the mid 15th century. The damages might include a pavilion on the top of the structure and a stone with the name of the structure carved in. The Mongolian invasion in the 13th century was a most likely cause. After the restoration, the structure suffered at least another attack. The damages on the top layer and the missing iron clamps were due to the later attack. The grooves and flat stones were to house holding device that affixed certain objects to the outer surface of the circular body. The metal or stone objects might have faced upward at the four corners of Chemseongdae, bridging the gaps between the rectangle layers and circular layers. The current Chemseongdae lost at least the four affixed objects, four holding devices, and one flat stone.