• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.217-217
• /
• 2016

The amorphous InGaZnO (a-IGZO) is widely accepted as a promising channel material for thin-film transistor (TFT) applications owing to their outstanding electrical properties [1, 2]. However, a-IGZO TFTs have still suffered from their bias instability with illumination [1-4]. Up to now, many researchers have studied the sub-gap density of states (DOS) as the root cause of instability. It is well known that defect states can influence on the performances and stabilities of a-IGZO TFTs. The defects states should be closely related with the deposition condition, including sputtering power, and pressure. Nevertheless, it has not been reported how these defects are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOIs) can be generated by electron attachment in oxygen atom near target surface and then accelerated up to few hundreds eV by a self-bias; at this time, the high energy bombardment of NOIs induce defects in oxide thin films. Recently, we have reported that the properties of IGZO thin films are strongly related with effects of NOIs which are generated during the sputtering process [5]. From our previous results, the electrical characteristics and the chemical bonding states of a-IGZO thin films were depended with the bombardment energy of NOIs. And also, we suggest that the deep sub-gap states in a-IGZO as well as thin film properties would be influenced by the bombardment of high energetic NOIs during the sputtering process.In this study, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process to prevent the NOIs bombardment effects and present how much to be improved the properties of a-IGZO thin film by this new deposition method. We deposited a-IGZO thin films by MFSS on SiO2/p-Si and glass substrate at various process conditions, after which we investigated the morphology, optical and electrical properties of the a-IGZO thin films.

• 공업화학
• /
• 제27권4호
• /
• pp.449-454
• /
• 2016

본 연구에서는 구형의 폴리스티렌 구슬을 틀로 사용하여, 크기분포가 좁으면서 속은 비어있고 벽이 다공성인 구조의 탄소 마이크로 캡슐을 합성하였다. 폴리스티렌의 표면은 무기물인 실리카졸이 쉽게 입혀질 수 있도록 폴리비닐피롤리돈(PVP)을 코팅하여 변조하였다. PVP가 코팅된 PS 마이크로 입자표면에 SBA-16 졸을 부착시킨 다음, 실리카층에 존재하는 중간 크기의 세공 내에 탄소원을 채워 넣는 음각식 형뜨기법을 적용함으로써 속이 빈 구조의 탄소 마이크로캡슐을 제조하였다. 탄화과정을 거치고 틀로 사용한 다공성 실리카입자를 HF로 용해하면, 좁은 입자크기분포를 갖는 중간세공이 함유된 계란껍질형의 탄소입자를 얻을 수 있었다. 계란껍질형 탄소 마이크로캡슐 입자의 다공성과 전기화학적 특성은 XRD, SEM, TEM, 질소분자 흡/탈착분석법 및 cyclic voltammetry법으로 평가하였다. 이들 탄소입자는 슈퍼캐패시터와 같은 전자재료로서 유효하게 사용될 만한 높은 전기전도도와 용량을 나타내었다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.160-160
• /
• 2015

InGaZnO (IGZO) thin-film transistors (TFTs) are very promising due to their potential use in high performance display backplane [1]. However, the stability of IGZO TFTs under the various stresses has been issued for the practical IGZO applications [2]. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability [3]. Nomura et al. reported that these deep defects are located in the surface layer of the IGZO channel [4]. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process [5]. It is well known that these trap states can influence on the performances and stabilities of IGZO TFTs. Nevertheless, it has not been reported how these defect states are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films [6-10] and can change the defect states of IGZO thin film. In this study, we have confirmed that the NOIs accelerated by the self-bias were one of the dominant causes of instability in IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process [9-10] to eliminate the NOI bombardment effects and present how much to be improved the instability of IGZO TFTs by this new deposition method.

• 한국재료학회지
• /
• 제20권6호
• /
• pp.312-318
• /
• 2010

Multilayer Poly methyl methacrylate (PMMA)/ Poly vinyl alcohol (PVA) bone plates were fabricated using electrospinning and in vitro investigations were carried out for pre-clinical biocompatibility studies. The initial cellular cytotoxicity of the methacrylate (PMMA)/ Poly vinyl alcohol (PVA) bone plates was measured by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay using fibroblast-like L-929 cells. Cellular adhesion and differentiation studies were carried out using osteoblast-like MG-63 cells. As simulated body fluid (SBF) contains the same ionic concentration of body fluid and any bioactive material tends to deposit bone-like apatite on the samples surfaces into the SBF, in vitro bioactivity of the multilayer bone plates were investigated using SBF. We also studied the internal organization and tensile strength of the multilayer PMMA/PVA bone plates using micro-computed topography (${\mu}$-CT) and universal testing instrument (UTI, Korea) respectively. The cellular cytotoxicity study with MTT confirmed that the cellular viability was 78 to 90% which indicates good cyto-compatibility. Scanning electron microscopic findings revealed a good attachment and adhesion phenomenon of MG-63 cells onto the surfaces of the samples. Cellular differentiation studies also showed that osteogenic differentiation was switched on in a timely manner and affirmed along with that of the control group. Bone-like apatite formation on the surfaces was confirmed within 14 days of SBF incubation. Initial organizations of the multilayer PMMA/PVA bone plates were characterized as dense and uniform. The tensile strength of the post-pressing electronspun mat was higher than that of the pre-electronspun mat. These results suggest that a multilayer PMMA/PVA bone plate system is biocompatible, bioactive and a very good alternative bone plate system.

• 한국융합학회논문지
• /
• 제6권3호
• /
• pp.119-125
• /
• 2015

본 연구의 목적은 가족의 기능적 결손이라는 위험상황에서 위험요인, 보호요인, 심리적응 간의 관계를 검증하고, 심리적응 수준이 높은 청소년을 보호해주는 보호요인을 파악하고자 한다. 이를 위해 한국국청소년정책연구원(2008)에서 조사한 한국청소년패널조사 중2 패널 5차년도 자료를 가지고 기술통계 분석과 로지스틱 회귀 분석을 실시하였다. 연구결과 청소년의 보호요인인 자아존중감과 학교친구애착에 따라 기능적 결손을 경험한 청소년의 심리적응 수준이 다르게 나타났다. 따라서 사회복지실천 현장에서 청소년의 위험요인에 초점을 맞추기보다는 위험요인을 완화시키는 과정이나 보호요인에 초점을 맞춤으로써 위험요인에 노출된 청소년을 바라보는 시각을 전환시킬 수 있으며 이들에 대한 개입도 달라질 것으로 판단된다.

• The Journal of Advanced Prosthodontics
• /
• 제7권3호
• /
• pp.191-198
• /
• 2015

PURPOSE. The purpose of this study was to compare the coronal bone level and patient satisfaction in 1-implant and 2-implant assisted mandibular overdentures. MATERIALS AND METHODS. Twenty patients who had maladaptive mandibular dentures were treated in this study. Patients were randomly divided into two groups. The first group received 1 implant (Simple line II, Implantium, South Korea) in their mandibular midline and the second group received 2 implants in their B and D regions (according to Misch's category). If the primary stability of each implant was at least 60 ISQ, ball attachment was placed and denture relined with soft liner. After 6 weeks, retentive cap incorporated with hard acrylic resin. In the 6 and 12 months recalls, periapical digital radiograph were made and visual analogue scale questionnaires were used to record patient satisfaction. The Friedman test was done for comparing the presurgical and postsurgical parameters in each group and the U-Mann Whitney test (P<.05) was done for comparison of post-treatment results between the two groups. RESULTS. All implants achieved sufficient primary stability to be immediately loaded. Patient satisfaction was high, and there were no significant differences between two groups (P>.05). In addition, mean marginal bone loss was $0.6{\pm}0.67$ mm in the first group and $0.6{\pm}0.51$ mm in the second group, after 12 month. Mean marginal bone loss showed no significant differences between two groups. CONCLUSION. This preliminary one-year result indicated that mandibular overdentures anchored to a single implant can be a safe and cost-effective method as a starting step for implant-overdenture treatment.

• Journal of Mechanical Science and Technology
• /
• 제18권8호
• /
• pp.1435-1450
• /
• 2004

Experimental data are presented which describe the effects of a combustor-level high free-stream turbulence on the near-wall flow structure and heat/mass transfer on the endwall of a linear high-turning turbine rotor cascade. The end wall flow structure is visualized by employing the partial- and total-coverage oil-film technique, and heat/mass transfer rate is measured by the naphthalene sublimation method. A turbulence generator is designed to provide a highly-turbulent flow which has free-stream turbulence intensity and integral length scale of 14.7% and 80mm, respectively, at the cascade entrance. The surface flow visualizations show that the high free-stream turbulence has little effect on the attachment line, but alters the separation line noticeably. Under high free-stream turbulence, the incoming near-wall flow upstream of the adjacent separation lines collides more obliquely with the suction surface. A weaker lift-up force arising from this more oblique collision results in the narrower suction-side corner vortex area in the high turbulence case. The high free-stream turbulence enhances the heat/mass transfer in the central area of the turbine passage, but only a slight augmentation is found in the end wall regions adjacent to the leading and trailing edges. Therefore, the high free-stream turbulence makes the end wall heat load more uniform. It is also observed that the heat/mass transfers along the locus of the pressure-side leg of the leading-edge horseshoe vortex and along the suction-side corner are influenced most strongly by the high free-stream turbulence. In this study, the end wall surface is classified into seven different regions based on the local heat/mass transfer distribution, and the effects of the high free-stream turbulence on the local heat/mass transfer in each region are discussed in detail.

• 한국재난정보학회 논문집
• /
• 제14권2호
• /
• pp.154-164
• /
• 2018

연구목적 : 최근 기후변화에 따라 여름철 태풍, 호우와 겨울철 대설, 한파 등의 기상재난이 증가하고 있다. 대설재난은 교통, 건물, 시설물 등에 다양한 피해를 발생시키기 때문에 신속한 대처가 필요하다. 대설재난이 도시 안전에 영향을 주고 있으나 우리나라의 대설재난 대처는 미흡하고, 정책 연구도 부족한 상황이다. 연구방법 : 본 연구는 대설재난이 발생할 때 신속한 도로 제설을 위하여 제설차량과 장비에 정보 통신 기술을 활용한 사례를 분석하고, 시사점을 도출한다. 연구결과 : 도로 제설장비에 정보통신기술이 적용된 장비를 부착하면 긴급 상황시 제설차량과 장비의 위치를 파악하여 인근지역의 도로 제설을 응원할 수 있다. 결론 : 본 연구의 사례 분석은 향후 지자체 제설장비의 효율적 이용을 위해 활용될 수 있다.

• Biomolecules & Therapeutics
• /
• 제24권3호
• /
• pp.260-267
• /
• 2016

Mesenchymal stem cells (MSCs) offer significant therapeutic promise for various regenerative therapies. However, MSC-based therapy for injury exhibits low efficacy due to the pathological environment in target tissues and the differences between in vitro and in vivo conditions. To address this issue, we developed adipose-derived MSC spheroids as a novel delivery method to preserve the stem cell microenvironment. MSC spheroids were generated by suspension culture for 3 days, and their sizes increased in a time-dependent manner. After re-attachment of MSC spheroids to the plastic dish, their adhesion capacity and morphology were not altered. MSC spheroids showed enhanced production of hypoxia-induced angiogenic cytokines such as vascular endothelial growth factor (VEGF), stromal cell derived factor (SDF), and hepatocyte growth factor (HGF). In addition, spheroid culture promoted the preservation of extracellular matrix (ECM) components, such as laminin and fibronectin, in a culture time- and spheroid size-dependent manner. Furthermore, phosphorylation of AKT, a cell survival signal, was significantly higher and the expression of pro-apoptotic molecules, poly (ADP ribose) polymerase-1 (PARP-1) and cleaved caspase-3, was markedly lower in the spheroids than in MSCs in monolayers. In the murine hindlimb ischemia model, transplanted MSC spheroids showed better proliferation than MSCs in monolayer. These findings suggest that MSC spheroids promote MSC bioactivities via secretion of angiogenic cytokines, preservation of ECM components, and regulation of apoptotic signals. Therefore, MSC spheroid-based cell therapy may serve as a simple and effective strategy for regenerative medicine.

• Journal of Chest Surgery
• /
• 제36권9호
• /
• pp.633-637
• /
• 2003

일시적인 삼첨판 절개법은 좋은 시야를 제공하고 심실을 열지 않고 심실중격결손의 폐쇄수술을 할 수 있다. 그러나 대부분의 외과의는 삼첨판막의 폐쇄부전의 염려로 주저하게 된다. 특히 최근의 교과서에서는 일시적인 삼첨판 절개법은 장기성적의 발표가 예외적인 방법으로만 기술되어 있고 더 이상의 분석이나 기술이 되어 있지 않다. 대상 및 방법: 1985년부터 1994년까지 수술받은 11명으로부터 술 전의 자료, 술 후 경과, 최근 심초음파와 심전도를 토대로 후향적 연구를 시행하였다. 결과: 심초음파에서 삼첨판폐쇄부전은 없는 경우가 9명, 미세한(trivial) 경우가 2명이었고, 심전도상 의미있는 심전도블록은 없었다. 결론: 삼첨판 절개법은 심실중격결손의 폐쇄수술을 시행하는 데 안전하며 향상된 시야를 제공하는 데 효과적인 방법이며, 삼첨판 이상이나 심전도상에 나쁜 영향을 끼치지 않는다.