• 한국패류학회지
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• 제20권1호
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• pp.1-6
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• 2004

An anatomical and ultrastructural study on the dart sac and the dart of a Korean snail Nesiohelix samarangae was conducted to understand their morphological characteristics with the help of the light microscope and electron microscopes, TEM and SEM. Nesiolelix samarangae had two darts which are pure white structures 6-8 mm in length, tapering from 0.6-0.8 mm to 0.15-0.3 mm. The dart sac had a long conic lumen subdivided into two by a septal wall, and the darts were centrally embedded in the thick muscular layers of the sac. The darts occupied each of the two luminal spaces one per each. The convexed surfaces of the darts had many crystal buds in the shape of the petals. Otherwise, the convexed surfaces of the darts had numerous crystal buds in the shape of candle or topaz. The luminal surface of the dart sac was covered with a single columnar epithelium. The epithelial cells possessed microvilli on their free surface.

• 한국전기전자재료학회논문지
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• 제26권11호
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• pp.821-825
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• 2013

Effect of multi-stacked layer (MSL), 0.1 mol (M) and 0.3 mol (M) hafnium oxide ($HfO_2$) alignment layers were fabricated via a solution-process for LCs orientation. The solutions were spin-coated and annealed in a furnace. MSL consists of three sub-layers using 0.1 M solution, mono-layer (ML) is composed of 0.3 M $HfO_2$ solution. Then ion-beam irradiation was treated with 1.8 keV for 2 min. $HfO_2$-based LC cells were investigated through photographs, pre-tilt angle using crystal rotation method, X-ray photoelectron spectroscopy (XPS) measurement, and surface roughness using atomic force microscopy(AFM) for their characteristic research. Good LC orientation characteristics were observed on MSL $HfO_2$ surface. The LC alignment mechanism on MSL $HfO_2$ and ML $HfO_2$ surfaces was attributed to van der Waals (VDW) interaction between the LC molecular and substrate surface.

• 한국결정성장학회지
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• 제32권2호
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• pp.51-54
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• 2022

연료전지에 사용되는 귀금속 전류집전체의 물성은 소재 기공도에 크게 영향을 받는다. 따라서 소재 기공도를 제어 위한 다양한 노력들이 진행되어왔다. 이중 많이 사용되는 전략으로 재료 열처리 시 기공형성제를 첨가하는 것이다. 기존의 기공형성제는 3차원 구조체였다. 본 연구에서는 차별화 전략으로 Ag 전류집전체의 기공도를 높이기 위해 2차원 구조 나노시트를 소결방지제로 첨가하였다. 실제로 나노시트 첨가에 의해 소결밀도가 감소되는 것을 보여주었다. 2차원 소재로는 초나노 두께(~ 1 nm)를 갖는 RuO₂ 나노시트가 이용되었다.

• Elastomers and Composites
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• 제58권1호
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• pp.1-10
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• 2023

In this study, we investigate the liquid crystal (LC) alignment of LC cells created from plant-based polysaccharide derivatives, such as guar gum. Guar gum films exhibit satisfactorily high optical transparency in the visible light region (400-750 nm). For example, the transmittance of polyimide films, which are the most typically used LC alignment layers, is 87%, whereas that of guar gum films deposited onto a glass substrate at a wavelength of 550 nm is approximately 99%. The observed LC alignment depends on the rubbing depth. For example, an LC cell comprising a guar gum film fabricated via rubbing at rubbing depths of 0.1, 0.2, 0.3, and 0.4 mm exhibits a planar LC alignment, whereas it exhibits a vertical LC alignment at a rubbing depth of 0.5 mm. Additionally, the LC alignment is shown to be correlated with the total surface energy of the guar gum films. When the total surface energy of a rubbed guar gum film exceeds 58.10 mJ/m², an LC cell comprising the guar gum film exhibits a stable and vertical LC alignment. Therefore, guar gum can be used to realize the vertical alignment system of LC via a simple adjustment of the rubbing depth.

• 한국결정성장학회지
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• 제7권1호
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• pp.81-92
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• 1997

전극함몰형 태양전지에 후면 부유접합의 도입은 양질의 표면보호를 제공할 수 있어서 효율 향상을 꾀할 수 있다. 이 논문은 PC-1D 모델링을 통하여 후면 부유접합형 태양전지의 효율을 시뮬레이션 분석한 것이다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권1호
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• pp.53-60
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• 2014

Different kinds of post-deposition annealing (PDA) by a rapid thermal process (RTP) are used to enhance the field-effect passivation of $Al_2O_3$ film in crystal Si solar cells. To characterize the effects of PDA on $Al_2O_3$ and the interface, metal-insulator semiconductor (MIS) devices were fabricated. The effects of PDA were characterized as functions of RTP temperature from $400{\sim}700^{\circ}C$ and RTP time from 30~120 s. A high temperature PDA can retard the passivation of thin $Al_2O_3$ film in c-Si solar cells. PDA by RTP at $400^{\circ}C$ results in better passivation than a PDA at $400^{\circ}C$ in forming gas ($H_2$ 4% in $N_2$) for 30 minutes. A high thermal budget causes blistering on $Al_2O_3$ film, which degrades its thermal stability and effective lifetime. It is related to the film structure, deposition temperature, thickness of the film, and annealing temperature. RTP shows the possibility of being applied to the PDA of $Al_2O_3$ film. Optimal PDA conditions should be studied for specific $Al_2O_3$ films, considering blistering.

• Current Photovoltaic Research
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• 제3권1호
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• pp.21-26
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• 2015

High efficiency $Cu(In,Ga)Se_2$ solar cells are generally prepared above $500^{\circ}C$. Lowering the process temperature can allow wider selection of substrate material and process window. In this paper, the three-stage co-evaporation process widely used to grow CIGS thin film at high temperature was modified to reduce the maximum substrate temperature. Below $400^{\circ}C$ the CIGS films show poor crystal growth and lower solar cell performance, in spite of external Na doping by NaF. As a new approach, Cu source instead of Cu with Se in the second stage was applied on the $(In,Ga)_2Se_3$ precursor at $400^{\circ}C$ and achieved a better crystal growth. The distribution of Ga in the films produce by new method were investigated and solar cells were fabricated using these films.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.464.1-464.1
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• 2014

Among numerous material candidates, Cu(InxGa1-x)(SySe2-y) (CIGS) thin films have emerged as promising material candidates for thin film solar cell applications due to the high energy conversion efficiency and relatively low fabrication cost. The CIGS thin film solar cells consist of several materials, including Mo back contacts, ZnO-based window layers, and CdS buffer layers. All these materials have different crystal structures and contain quite distinct chemical elements, and hence the device characterization requires careful analyses. Most of all, identification of the major trap states resulting in the carrier recombination processes is a key step toward realization of high efficiency CIGS solar cells. We have carried out electrical investigations of CIGS thin film solar cells to specify the major trap states and their roles in photovoltaic performance. In particular, we have used the temperature-dependent transport characterizations and admittance spectroscopy. In this presentation, we will introduce some exemplary studies of DC and AC electrical characteristics of the CIGS solar cells.

• Integrative Medicine Research
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• 제6권1호
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• pp.12-18
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• 2017

Cryopreservation is a process that preserves organelles, cells, tissues, or any other biological constructs by cooling the samples to very low temperatures. The responses of living cells to ice formation are of theoretical interest and practical relevance. Stem cells and other viable tissues, which have great potential for use in basic research as well as for many medical applications, cannot be stored with simple cooling or freezing for a long time because ice crystal formation, osmotic shock, and membrane damage during freezing and thawing will cause cell death. The successful cryopreservation of cells and tissues has been gradually increasing in recent years, with the use of cryoprotective agents and temperature control equipment. Continuous understanding of the physical and chemical properties that occur in the freezing and thawing cycle will be necessary for the successful cryopreservation of cells or tissues and their clinical applications. In this review, we briefly address representative cryopreservation processes, such as slow freezing and vitrification, and the available cryoprotective agents. In addition, some adverse effects of cryopreservation are mentioned.

• 한국재료학회지
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• 제32권2호
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• pp.94-97
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• 2022

We fabricated 3 types of ETL, mp TiO₂, ZnO, and ZnO coated on mp TiO₂(ZMT) to compare the photoelectric conversion efficiency (PCE) and fill factor (FF) of Perovskite solar cells. The structure of the cells was FTO/ETL/Perovskite (CH₃NH₃PbI₃)/spiro-MeOTAD/Ag. SEM morphology assessment of the ETLs showed that mp TiO₂ was porous, ZnO was flat, and the ZMT porous surface was filled with a thin layer. Via XRD measurements, the crystal structures of mp TiO₂ and ZnO ETL were found to be anatase and wurtzite, respectively. The XPS patterns showing energy bonding of mp TiO₂, ZnO, and ZMT O 1s confirmed these materials to be metal oxides such as ETL. The electrical characteristics of the Perovskite solar cells were measured using a solar simulator. Perovskite solar cells with ZMT ETL showed showed PCE of 10.29 % than that of conventional mp TiO₂ ETL devices. This was considered a result of preventing Perovskite from seeping into the ETL and preventing recombination of electrons and holes.