• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.96-104
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• 2010

We suggest here a cost-effective replica fabrication method for transparent and hard molds for imprinting lithography such as NIL and S-FIL. The process starts with the use of a replica hard mold from a master, using a polymer copy as a carrier. The polymer copy as a carrier was treated by soluble process for forming anti-adhesion layer. Duplicated hard molds can eliminate direct contact between a hard master and a patterned polymer on a substrate and the generated contamination of a master during the imprinting process. The replica hard mold exhibits the glass-like properties introduced here, such as transparency and hardness, make it appropriate for nanoimprint lithography and step-and-flash imprint lithography.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.262-267
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• 2016

In this study, we present an excellent approach for easily and uniformly immobilizing Pt, Au and bimetallic PtAu nanoparticles (NPs) on a multi-walled carbon nanotube (MWNT)-coated layer through dry plasma reduction. The NPs are stably and uniformly immobilized on the surface of MWNTs and the nanohybrid materials are applied to counter electrode (CE) of dye-sensitized solar cells (DSCs). The electrochemical properties of CEs are examined through cyclic voltammogram, electrochemical impedance spectroscopy, and Tafel measurements. As a result, both electrochemical catalytic activity and electrical conductivity are highest for PtAu/MWNT electrode. The DSC employing PtAu/MWNT CE exhibits power conversion efficiency of 7.9%. The efficiency is better than those of devices with MWNT (2.6%), AuNP/MWNT (2.7%) and PtNP/MWNT (7.5%) CEs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.6
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• pp.628-636
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• 2014

This paper describes the design and analysis of five-element planar array antenna of an anti-jamming satellite navigation system. We propose a design of multi-layer patch antenna for Global Positioning System(GPS) $L_1/L_2$ dual bands. The proposed antenna has two ports feeding network with a hybrid chip coupler for a broad bandwidth with Right-Handed Circular Polarization(RHCP). The measurement results show the bore-sight gains of 1.10 dBic($L_1$) and 0.37 dBic($L_2$) for the center element. The bore-sight gains of an edge element are 0.99 dBic($L_1$) and -0.57 dBic($L_2$). At a fixed elevation angle of $30^{\circ}$, antennas show average gains of -2.08 dBic ($L_1$) and -5.33 dBic($L_2$) for the center element, and average gains of -0.40 dBic($L_1$) and -2.09 dBic($L_2$) for the edge elements. The results demonstrate that the proposed array antenna is suitable for anti-jamming applications.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.19-27
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• 1993

Capacitive pressure sensor for low pressure measurements has been fabricated by using $n^{+}$ epitaxial layer electrochemical etching stop and glass-to-silicon electrostatic bonding technique. The sensor had hybrid configuration of a sensor chip, which consists of sensor capacitor and reference capacitor, and two output signal detection IC chips. A fabricated sensor, with a $1.0{\times}1.0 mm^{2}$ square size and a $10{\mu}m$ thick flat diaphragm, showed a 7.1 pF zero pressure capacitance, and 5.2 % F.S, sensitivity in 10 KPa pressure range. By using a capacitance to voltage converter, the thermal zero shift of 0.051 %F.S./$^{\circ}C$ and the thermal sensitivity shift of 0.12 %F.S./$^{\circ}C$ for temperature range of $5{\sim}45^{\circ}C$ were obtained.

• Journal of Broadcast Engineering
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• v.23 no.2
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• pp.316-319
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• 2018

When a terrestrial UHD broadcasting service and a mobile HD broadcasting service are provided using the PLP function provided by ATSC 3.0 and domestic UHD broadcasting standard, a small amount of data may be additionally transmitted to further provide high quality UHD-3D broadcasting service. The left and right images of the stereoscopic image are input, one view image is encoded by the SHVC method, and the other view images are encoded by the SHVC method of the two-view cross-referencing method. However, since the base layers (BL) of the two encoders are mutually common, the two encoders correspond to encoders that generate one BL stream and two enhancement layer (EL) streams. The average encoding efficiency is 16% more efficient compared to the third independent HEVC encoding for the UHD-3D broadcast service. The proposed scheme reduces the fluctuation of PSNR per image frame and increases the image quality of minimum PSNR frame by 0.6dB.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.77.1-77.1
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• 2013

Atomic layer deposition (ALD) is known for its self-limiting reaction, which offers atomic-level controllability of the growth of thin films for a wide range of applications. The self-limiting mechanism leads to very useful properties, such as excellent uniformity over a large area and superior conformality on complex structures. These unique features of ALD provide promising opportunities for future electronics. Although the ALD of Al2O3 film (using trimethyl-aluminum and water as a metal precursor and oxygen source, respectively) can be regarded as a representative example of an ideal ALD based on the completely self-limiting reaction, there are many cases deviating from the ideal ALD reaction in recently developed ALD processes. The nonconventional aspects of the ALD reactions may strongly influence the various properties of the functional materials grown by ALD, and the lack of comprehension of these aspects has made ALD difficult to control. In this respect, several dominant factors that complicate ALD reactions, including the types of metal precursors, non-metal precursors (oxygen sources or reducing agents), and substrates, will be discussed in this presentation. Several functional materials for future electronics, such as higher-k dielectrics (TiO2, SrTiO3) for DRAM application, and resistive switching materials (NiO) for RRAM application, will be addressed in this talk. Unwanted supply of oxygen atoms from the substrate or other component oxide to the incoming precursors during the precursor pulse step, and outward diffusion of substrate atoms to the growing film surface even during the steady-state growth influenced the growth, crystal structure, and properties of the various films.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.487-501
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• 1998

In the case of CAD/CAM ceramic inlay restorations, if isthmus width is widened too much, it may cause fracture of remaining tooth structure or loss of bonding at the luting interface because of excessive displacement of buccal or lingual cusps under occlusal loads. So to clarify the criterior of widening isthmus width, this study was designed to test the tensile bond strength and bond failure mode between dentin and ceramic cemented with luting composite resin cements. Cylindrical ceramic blocks(Vita Cerec Mark II, d=4mm) were bonded to buccal dentin of 40 freshly extracted third molars with 4 luting composite resin cements(group1 : Scotchbond Resin Cement/Scotchbond Multi-Purpose, group2 : Duolink Resin Cement/ All-Bond 2, group3: Bistite Resin Cement/Ceramics Primer, and group4:Superbond C&B). Tensile bond test was done under universal testing machine using bonding and measuring alignment blocks(${\phi}ilo$ & Urn, 1992). After immersion of fractured samples into 1 % methylene blue for 24 hours, failure mode was analysed under stereomicroscope and SEM. Results: The tensile bond strength of goup 1, 2 & 4 was $13.97{\pm}2.90$ MPa, $16.49{\pm}3.90$ MPa and $16.l7{\pm}4.32$ MPa, respectively. There was no statistical differences(p>0.05). But, group 3 showed significantly lower bond stregnth($5.98{\pm}1.l7$ MPa, p<0.05). In almost all samples, adhesive fractures between dentin and resin cements were observed. But, in group 1, 2 & 4, as bond strength increased, cohesive fracture within resin cement was observed simultaneously. And, in group 3, as bond strength decreased, cohesive fracture between hybrid layer and composite resin cement was also observed. Cohesive fracture within dentin and porcelain adhesive fracture were not observed. In conclusion, although adhesive cements were used in CAD/CAM -fabricated ceramic inlay restorations, the conservative priciples of cavity preparation must be obligated.

• Journal of Ocean Engineering and Technology
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• v.30 no.5
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• pp.356-360
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• 2016

Recently, the lifetime extension of nuclear power plants has been considered. Thus, it is necessary to consider facility safety management and economic management. However, when the bolts in nuclear power plants are replaced and the turbines of nuclear power plant are disassembled, numerous problems are found in relation to stuck bolts in clamping parts. In order to solve these problems, a hybrid vacuum chamber was first designed and manufactured. It can perform arc ion plating and sputtering, which were used to deposit Ti/TiN on an A913 B7 bolt. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted to determine the composition and characteristics of the bolt, and tests were conducted to determine how long the bolt could endure under various conditions in a nuclear power plant. The SEM and XRD results clearly showed a continual and even coating layer. When this TiN-coated bolt is used in a nuclear power plant, the lifetime can be extended compared to a conventional bolt, but it is necessary to determine what additional properties are required.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.105-105
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• 2019

보나 여수로와 같은 수공구조물의 주변에서 발생하는 흐름 거동은 구조물 모서리에서 발생하는 흐름분리(flow separation)와 이에 따른 전단층(shear layer)과 재순환(recirculation) 흐름 영역의 발달 그리고 분리된 흐름의 재부착(reattachment)이 특징이다. 공학적으로 난류의 해석에 있어서 이러한 흐름 거동들을 정확하게 예측하는 것은 수공구조물 설계에 있어서 중요하다. 이 연구에서는 흐름 분리와 재순환 영역의 발달 그리고 흐름 재부착을 포함하는 후방계단(backward-facing step) 흐름을 155,000의 레이놀즈수 조건에서 하이브리드 RANS/LES 모델을 적용하여 해석결과를 평가한다. 하이브리드 모델로는 벽에 인접한 격자의 해상도에 상대적으로 민감하지 않은 SST(shear-stress transport) 난류 모델을 이용하는 DES(detached-eddy simulation) 기법을 적용하였다. 계단 높이가 h인 계산영역은 흐름방향 길이가 34h, 높이는 계단 상류와 하류에서 각각 1h와 2h 그리고 폭은 $2{\pi}$이다. 계단은 상류단으로부터 10h 하류부 지점에 위치한다. 경계조건으로 상부와 하부 벽면에 대해서는 비활조건을 적용한다. 상류부 수로에서 완전 발달한 흐름을 재현하기 위해서 유입경계조건은 유입부 하류 $2{\pi}h$ 지점에서 계산된 유속과 난류량을 매핑(mapping)기법을 이용하여 반복적으로 적용한다. 총 3.1백만개와 7.3백만개의 셀로 계산영역을 구현한 두 개의 계산격자 그리고 약 3.1백만개의 셀을 이용했지만 벽면 근처에서의 격자 구성을 다른 방식으로 설정한 두 가지 격자를 이용하여 격자 해상도가 DES 수치해석 결과에 미치는 영향을 분석하였다. 수치해석결과는 본 연구에서 상류단 조건으로 적용한 매핑기법이 대상 수로에서 완전 발달한 흐름을 잘 재현함을 보여주며, 합리적인 DES 해석 결과를 얻기 위해서는 벽에 수직한 방향으로 적절한 격자의 해상도와 분포가 필요함을 보여준다.

• Current Applied Physics
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• v.18 no.12
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• pp.1564-1570
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• 2018

Charge transport dynamics in ZnO based inverted organic solar cell (IOSC) has been characterized with transient photocurrent spectroscopy and localised photocurrent mapping-atomic force microscopy. The value of maximum exciton generation rate was found to vary from $2.6{\times}10^{27}m^{-3}s^{-1}$ ($J_{sat}=79.7A\;m^{-2}$) to $2.9{\times}10^{27}m^{-3}s^{-1}$ ($J_{sat}=90.8A\;m^{-2}$) for devices with power conversion efficiency ranging from 2.03 to 2.51%. These results suggest that nanorods served as an excellent electron transporting layer that provides efficient charge transport and enhances IOSC device performance. The photovoltaic performance of OSCs with various growth times of ZnO nanorods have been analysed for a comparison between AM1.5G spectrum and local solar spectrum. The simulated PCE of all devices operating under local spectrum exhibited extensive improvement with the gain of 13.3-3.7% in which the ZnO nanorods grown at 15 min possess the highest PCE under local solar with the value of 2.82%.