• Applied Microscopy
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• 제46권3호
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• pp.160-163
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• 2016

Effect of dealloying condition on the formation of nanoporous structure in melt-spun $Al_{60}Ge_{30}Mn_{10}$ alloy has been investigated in the present study. In as-melt-spun $Al_{60}Ge_{30}Mn_{10}$ alloy spinodal decomposition occurs in the undercooled liquid during cooling, leading to amorphous phase separation. By immersing the as-melt-spun $Al_{60}Ge_{30}Mn_{10}$ alloy in 5 wt% HCl solution, Al-rich amorphous region is leached out, resulting in an interconnected nano-porous $GeO_x$ with an amorphous structure. The dealloying temperature strongly affects the whole dealloying process. At higher dealloying temperature, dissolution kinetics and surface diffusion/agglomeration rate become higher, resulting in the accelerated dealloying kinetics, i.e., larger dealloying depth and coarser pore-ligament structure.

• Applied Microscopy
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• 제45권3호
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• pp.131-134
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• 2015

Here we show how by processing energy dispersive X-ray spectrometry (EDS) data obtained using highly sensitive, new generation EDS detectors in the AZtec LayerProbe software we can obtain data of sufficiently high quality to non-destructively measure the number of layers in two-dimensional (2D) $MoS_2$ and $MoS_2/WSe_2$ and thereby enable the characterization of working devices based on 2D materials. We compare the thickness measurements with EDS to results from atomic force microscopy measurements. We also show how we can use electron backscatter diffraction (EBSD) to address fabrication challenges of 2D materials. Results from EBSD analysis of individual flakes of exfoliated $MoS_2$ obtained using the Nordlys Nano detector are shown to aid a better understanding of the exfoliation process which is still widely used to produce 2D materials for research purposes.

• 동양고전연구
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• 제57호
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• pp.383-406
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• 2014

미암(眉巖) 유희춘(柳希春)(1513~1577)은 시를 생활의 일부로 여겼다. 그러므로 필자는 미암 유희춘의 한시에 초점을 맞추어 살펴보았다. 본고에서 논의한 사항들을 종합하여 결론으로 삼으면 다음과 같다. 미암(眉巖)은 문학을 재도적(載道的) 관점에서 이해하려고 하였다. 미암(眉巖)의 한시는 현재 300여수로 추산되는데, 필자가 파악한 작품은 285수이다. 그리고 미암(眉巖)은 진지한 자세로 작시(作詩)에 임했으며, 형식보다는 내용을 중시하였다. 고시(古詩) 율시(律詩) 절구(絶句) 가운데 絶句(특히 칠언(七言))가 가장 많으며, 오언(五言)보다 칠언(七言)을 더 선호한 것으로 보인다. 고시(古詩)의 경우, 전고(典故)가 비교적 많은 편이다. 절구(絶句)는 미암(眉巖)이 가장 능했던 시체(詩體)로, 주로 생활과 관련된 내용들이 주류를 이루고 있다. 그리고 율시(律詩)는 자기성찰이나 현실세계에 대한 자신의 심정을 표출한 내용의 시들이 많다. 미암(眉巖)의 시는 유배기와 해배 복관 이후기로 나눌 수 있다. 유배기는 학문 연마를 통한 자기수양(自己修養), 우정(友情), 애민(愛民) 등으로, 해배 복관 이후기는 충군(忠君), 지인(知人)들과의 교유, 감회(感懷), 숭조상문(崇祖尙門), 자기성찰(自己省察), 문학적 교감을 통한 부부애(夫婦愛) 등으로 나눌 수 있다. 미암(眉巖)의 시는 시제(詩題)에 음(吟) 송(送) 차운(次韻) 등이 붙은 작품이 많으며, 일상생활이나 체험사실 등과 관련된 시들이 주류를 이루고 있다. 그리고 태반은 담담하게 사실 그대로를 자연스럽게 표현하고 있다. 미암(眉巖)은 시를 생활의 일부로 여겼으며, 부인 송덕봉과 일상생활에서 겪었던 일을 시로써 수창하며 서로 문학적 교감을 하였다는 점에서 주목할 만하다.

• Applied Microscopy
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• 제45권2호
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• pp.95-100
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• 2015

The in-situ heating transmission electron microscopy experiment allows us to observe the time- and temperature-dependent dynamic processes in nanoscale materials by examining the same specimen. The temperature, which is a major experimental parameter, must be measured accurately during in-situ heating experiments. Therefore, calibrating the thermocouple readout of the heating holder prior to the experiment is essential. The calibration can be performed using reference materials whose phase-transformation (melting, oxidation, reduction, etc.) temperatures are well-established. In this study, the calibration experiment was performed with four reference materials, i.e., pure Sn, Al-95 wt%Zn eutectic alloy, NiO/carbon nanotube composite, and pure Al, and the calibration curve and formula were obtained. The thermocouple readout of the holder used in this study provided a reliable temperature value with a relative error of <4%.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.131-134
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• 2009

We have developed a flexible OTFT backplane in which all the dielectrics are formed by solutionprocess in order to achieve low-cost and highthroughput manufacturing. The backplane successfully drives a flexible AM-OLED display with peak brightness of > 200 nit and the contrast ratio of > 1000:1 with great mechanical flexibility.

• 한국분말재료학회지
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• 제30권2호
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• pp.116-122
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• 2023

Because magnets fabricated using Nd-Fe-B exhibit excellent magnetic properties, this novel material is used in various high-tech industries. However, because of the brittleness and low formability of Nd-Fe-B magnets, the design freedom of shapes for improving the performance is limited based on conventional tooling and postprocessing. Laser-powder bed fusion (L-PBF), the most famous additive manufacturing (AM) technique, has recently emerged as a novel process for producing geometrically complex shapes of Nd-Fe-B parts owing to its high precision and good spatial resolution. However, because of the repeated thermal shock applied to the materials during L-PBF, it is difficult to fabricate a dense Nd-Fe-B magnet. In this study, a high-density (>96%) Nd-Fe-B magnet is successfully fabricated by minimizing the thermal residual stress caused by substrate heating during L-PBF.

• Transactions on Electrical and Electronic Materials
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• 제16권6호
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• pp.303-307
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• 2015

Multilayered films of ITO (In₂O₃:SnO₂ = 9:1)/SiO₂ were deposited on soda-lime glass by RF/DC magnetron sputtering at 500℃ to improve the energy conversion efficiency of dye-sensitized solar cells (DSSCs). The light absorption of the dye was improved by decrease in light reflectance from the surface of the DSSCs by using an ITO film. In order to estimate the optical characteristics and compare them with experimental results, a simulation program named EMP (essential macleod program) was used. EMP results revealed that the multilayered thin films showed high transmittance (approximate average transmittance of 79%) by adjusting the SiO₂ layer thickness. XRD results revealed that the ITO and TiO₂ films exhibited a crystalline phase with (400) and (101) preferred orientations at 2 θ = 26.24° and 35.18°, respectively. The photocurrent-voltage (I-V) characteristics of the DSSCs were measured under AM 1.5 and 100 mW/cm² (1 sun) by using a solar simulator. The DSSC fabricated on the ITO film with a 0.1-nm-thick SiO₂ film showed a Voc of 0.697 V, J_sc of 10.596 mA/cm² , FF of 66.423, and calculated power conversion efficiency (η_AM1.5) of 5.259%, which was the maximum value observed in this study.

• Fibers and Polymers
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• 제6권2호
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• pp.103-107
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• 2005

An attempt was made to correlate the polymerization temperature and rheological and thermal properties of acrylonitrile (AN)-acrylamide (AM) copolymers. The copolymers were synthesized at different polymerization temperature. The copolymer structure was characterized by gel permeation chromatography (GPC) and Infrared spectrum (IR). The rheological and thermal properties were investigated by a viscometer and differential scanning calorimeter-thermogrametric (DSC-TG) analysis, respectively. When the polymerization temperature increased from $41^{\circ}C\;to\;65^{\circ}C$, the molecular weight $(\bar{M}_w)$ of copolymers decreased from 1,090,000 to 250,000, while its conversion increased from $18\%\;to\;63\%$, and the polymer composition changed slightly. To meet the requirements of carbon fibers, the rheological and thermal properties of products were also investigated. It was found that the relationship between viscosity and $\bar{M}_w$ was nonlinear and the viscosity index (n) decreased from 3.13 to 2.69, when the solution temperature increased from $30^{\circ}C\;to\;65^{\circ}C$. This suggests the dependence of viscosity upon $\bar{M}_w$ is higher at lower solution temperature. According to the result of activation energy, the sensivity of viscosity to solution temperature is higher for AN-AM copolymers synthesized at higher polymerization temperature. The result of thermal analysis shows that the copolymers obtained at higher polymerization temperature are easier to cyclization evidenced from lower initiation temperature. The weight loss behavior changed irregularly with polymerization temperature due to irregular change of liberation heat.

• 한국세라믹학회지
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• 제38권11호
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• pp.962-966
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• 2001

Crystal structure of PbBi$_2$Nb$_2$$O_{9}$ and $Sr_{1.2}$$Bi_{1.8}$Ta$_2$$O_{9}$ were determined by Rietveld method using neutron diffraction data in the temperature range of 300 K~1273K. Phase transition temperature were measured from the dielectric permittivitytemperature curve. The PbBi$_2$Nb$_2$$O_{9}$ showed a phase transition at about 810 K. In the Sr-excess compound $Sr_{1.2}$$Bi_{1.8}$Ta$_2$$O_{9}$ the phase transition was suppressed down to room temperature. Several structural models were tested by the Rietiveld refinement. Based on the \`R\` values and the structural parameters, the B2cb model is judged to be the most feasible one for the high temperature phase at above 810 K of the PbBi$_2$Nb$_2$$O_{9}$. The $Sr_{1.2}$$Bi_{1.8}$Ta$_2$$O_{9}$ sample was refined to show the most reliable results by the Am2m model.sults by the Am2m model.

• Applied Microscopy
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• 제45권3호
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• pp.107-114
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• 2015

Two-dimensional (2D) materials containing hole defects are a promising substitute for conventional nanopore membranes like silicon nitride. Hole defects on 2D materials, as atomically thin nanopores, have been used in nanopore devices, such as DNA sensor, gas sensor and purifier at lab-scale. For practical applications of 2D materials to nanopore devices, researches on characteristics of hole defects on graphene, hexagonal boron nitride and molybdenum disulfide have been conducted precisely using transmission electron microscope. Here, we summarized formation, features, structural preference and stability of hole defects on 2D materials with atomic-resolution transmission electron microscope images and theoretical calculations, emphasizing the future challenges in controlling the edge structures and stabilization of hole defects. Exploring the properties at the local structure of hole defects through in situ experiments is also the important issue for the fabrication of realistic 2D nanopore devices.