• 토지주택연구
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• 제7권4호
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• pp.281-289
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• 2016

압축 부재인 PHC 말뚝(직경 600mm)도 강선의 부착력을 높이면 83.6~91.6tonf의 극한 인장력에 대해 구조적으로 저항할 수 있는 것으로 실험결과 나타났다. 이러한 시험결과에 안전율을 고려하여 적절한 허용값을 제시하면 부상방지 앵커를 대체하거나 절감시킬 수 있는 것으로 기대되었다. 이를 위해서는 구조적 인장성능과 함께 실제 지반에 시공된 매입말뚝의 인발저항 거동이 규명되어야 한다. 본 연구에서는 현장에 시공된 실제 매입말뚝의 인발거동 특성을 파악하기 위하여 정적 인발재하시험을 실시하여 주면마찰력 산정식과 비교하였다. 또한, 간편하게 인발저항력을 평가하기 위하여 PDA를 이용한 동재하시험을 실시하여 정적 인발재하시험 결과와 비교하였다. 그 결과, 매입말뚝의 시멘트풀이 충분히 경화한 후인 15일 후에는 LH 주면마찰력 산정식의 마찰력과 정적인발재하시험결과가 잘 일치하였고 동재하시험에서 구한 마찰력과도 비교적 잘 일치하는 것으로 나타났다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.88-91
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• 2003

Tungsten is widely used as a plug for the multi-level interconnection structures. However, due to the poor adhesive properties of tungsten (W) on $SiO_2$ layer, the Ti/TiN barrier layer is usually deposited onto $SiO_2$ for increasing adhesion ability with W film. Generally, for the W-CMP (chemical mechanical polishing) process, the passivation layer on the tungsten surface during CMP plays an important role. In this paper, the effect of oxidants controlling the polishing selectivity of W/Ti/TiN layer were investigated. The alumina ($Al_2O_3$) abrasive containing slurry with $H_2O_2$ as the oxidizer, was studied. As our preliminary experimental results, very low removal rates were observed for the case of no-oxidant slurry. This low removal rate is only due to the mechanical abrasive force. However, for Ti and TiN with $H_2O_2$ oxidizer, different removal rate was observed. The removal mechanism of Ti during CMP is mainly due to mechanical abrasive, whereas for TiN, it is due to the formation of metastable soluble peroxide complex.

• 한국생산제조학회지
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• 제25권6호
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• pp.445-451
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• 2016

The Inconel 718 alloy is a well-known super-heat-resistant alloy and a difficult-to-cut material. Inconel 718 with excellent corrosion and heat resistance is used in harsh environments. However, the heat generated is not released owing to excellent physical properties, making processes (e.g., adhesion and thermal fatigue) difficult. Tool condition monitoring in machining is significant in reducing manufacturing costs. The cutting tool is easily broken and worn because of the material properties of Inconel 718. Therefore, tool management is required to improve tool life and machinability. This study proposes a method of predicting the tool wear with non-contacting sensors (e.g., IR thermometer for measuring the cutting temperature and a microphone for measuring the sound pressure level in machining). The cutting temperature and sound pressure fluctuation according to the tool condition and cutting force are analyzed using experimental data. This experiment verifies the effectiveness of the non-contact measurement signals in tool condition monitoring.

• 한국표면공학회지
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• 제45권6호
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• pp.257-263
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• 2012

CrN/AlN multilayer coatings with various bilayer periods in the range of 1.8 to 7.4 nm were synthesized using a closed-field unbalanced magnetron sputtering method. Their crystalline structure, chemical compositions and mechanical properties have been investigated with Auger electron spectroscopy, X-ray diffractometry, atomic force microscopy, nanoindentation, scratch tests. The properties of the multilayer coatings varied strongly depending upon the magnitude of the bilayer period. The multilayer coating with a bilayer period of 1.8 nm showed the maximum hardness and an elastic modulus of approximately 37.6 and 417 GPa, respectively, which was 1.54 times higher than the hardness predicted by the rule of mixture from the CrN and AlN coatings. The hardness of the multilayer coating increased as the bilayer period decreased, i.e. as the rotation speed increased. The Hall-Petch type relationship, hardness being related to (1/periodicity)$^{-1/2}$, suggested by Lehoczky was confirmed for the CrN/AlN multilayer coatings with bilayer period close to the 5-10 nm range. With decreasing bilayer period, the surface morphology of the films became rougher and the critical load of films for adhesion strength gradually decreased.

• Macromolecular Research
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• 제17권7호
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• pp.458-463
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• 2009

Polyurethane (PU) is widely used as a cardiovascular biomaterial due to its good mechanical properties and hemocompatibility, but it is not adhesive to endothelial cells (ECs). Cell adhesive peptides, GRGDS and YIGSR, were found to promote adhesion and spreading of ECs and showed a synergistic effect when both of them were used. In this study, a surface modification was designed to fabricate an EC-active PU surface capable of promoting endothelialization using the peptides and poly(ethylene glycol) (PEG) spacer, The modified PU surfaces were characterized in vitro. The density of the grafted PEG on the PU surface was measured by acid-base back titration to the terminal-free isocyanate groups. The successful immobilization of pep tides was confirmed by amino acid analysis, following hydrolysis, and contact angle measurement. The uniform distribution of peptides on the surface was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). To evaluate the EC adhesive property, cell viability test using human umbilical vein EC (HUVEC) was investigated in vitro and enhanced endothelialization was characterized by the introduction of cell adhesive peptides, GRGDS and YIGSR, and PEG spacer. Therefore, GRGDS and YIGSR co-immobilized PU surfaces can be applied to an EC-specific vascular graft with long-term patency by endothelialization.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.552-552
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• 2013

In our study we consider Al2O3 ceramic substrates for Plasma Surface Treatments in order to improve deposited diamond surface and increase diamond deposition rate by applying DBD (Dielectric Barrier Dischrge) system. Because Plasma Surface Treatments was used as a modification method of material surface properties like surface free energy, wettability, and adhesion. By applying Plasma Surface Treatments diamond films are deposited on the Al2O3 ceramic substrates. DC Arc Plasmatron with mathane and hydrogen gases is used. Deposited diamond films are investigated by SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy) and XRD (X-ray Diffractometer). Then the C-H stretching of synthetic diamond films by FTIR (Fourier Transform Infrared Spectroscopy) is studied. As a result, nanocrystalline diamond films were identified by using SEM and diamond properties in XRD peaks at (111, $43.8{\Box}$, (220, $75.3{\Box}$ and (311, $90.4{\Box}$ were shown. Absorption peaks in FTIR spectrum, caused by CHx sp3 bond stretching of CVD diamond films, were identified as well. Finally, we improved such parameters as depostion rate ($2.3{\mu}m$/h), diamond surface uniformity, and impurities level by applying Plasma Surface Treatments. These experimental results show the importance of Plasma Surface Treatments for diamond deposition by a plasma source.

• Journal of Periodontal and Implant Science
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• 제42권6호
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• pp.248-255
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• 2012

Purpose: The aim of the present study was to evaluate the biological response of alkali- and heat-treated titanium-8tantalum-3niobium surfaces by cell proliferation and alkaline phosphatase (ALP) activity analysis. Methods: Commercial pure titanium (group cp-Ti) and alkali- and heat-treated titanium-8tantalum-3niobium (group AHT) disks were prepared. The surface properties were evaluated using scanning electron microscopy, energy dispersed spectroscopy and X-ray photoelectron spectroscopy (XPS). The surface roughness was evaluated by atomic force microscopy and a profilometer. The contact angle and surface energy were also analyzed. The biological response of fetal rat calvarial cells on group AHT was assessed by cell proliferation and ALP activity. Results: Group AHT showed a flake-like morphology microprofile and dense structure. XPS analysis of group AHT showed an increased amount of oxygen in the basic hydroxyl residue of titanium hydroxide groups compared with group cp-Ti. The surface roughness (Ra) measured by a profilometer showed no significant difference (P>0.05). Group AHT showed a lower contact angle and higher surface energy than group cp-Ti. Cell proliferation on group AHT surfaces was significantly higher than on group cp-Ti surfaces (P<0.05). In comparison to group cp-Ti, group AHT enhanced ALP activity (P<0.05). Conclusions: These results suggest that group AHT stimulates osteoblast differentiation.

• Journal of Periodontal and Implant Science
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• 제43권4호
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• pp.198-205
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• 2013

Purpose: The aim of this study was to evaluate the surface properties and biological response of an anodized titanium surface by cell proliferation and alkaline phosphatase activity analysis. Methods: Commercial pure titanium (Ti) disks were prepared. The samples were divided into an untreated machined Ti group and anodized Ti group. The anodization of cp-Ti was formed using a constant voltage of 270 V for 60 seconds. The surface properties were evaluated using scanning electron microscopy, X-ray photoelectron spectroscopy, and an image analyzing microscope. The surface roughness was evaluated by atomic force microscopy and a profilometer. The contact angle and surface energy were analyzed. Cell adhesion, cell proliferation, and alkaline phosphatase activity were evaluated using mouse $MC_3T_3-E_1$ cells. Results: The anodized Ti group had a more porous and thicker layer on its surface. The surface roughness of the two groups measured by the profilometer showed no significant difference (P>0.001). The anodized Ti dioxide ($TiO_2$) surface exhibited better corrosion resistance and showed a significantly lower contact angle than the machined Ti surface (P>0.001). Although there was no significant difference in the cell viability between the two groups (P>0.001), the anodized $TiO_2$ surface showed significantly enhanced alkaline phosphatase activity (P<0.001). Conclusions: These results suggest that the surface modification of Ti by anodic oxidation improved the osteogenic response of the osteoblast cells.

• 대한기계학회논문집B
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• 제35권11호
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• pp.1229-1235
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• 2011

본 연구에서는 세포의 성장속도, 배양표면 부착, 체내 특이성을 유지에 중요한 요소인 세포외 기질 물질에 따른 심근세포주(HL-1 cell)의 성장, 생존률 및 표현형 등을 분석했다. 서로 다른 5 가지의 세포외 기질 환경을 조성하여 세포 성장에 미치는 영향에 대하여 분석했다. 세포외 기질 물질이 처리된 배양 표면의 물리적인 형태는 원자현미경을 통하여 분석했으며, 세포의 표면부착, 성장 및 증식과 생존률 및 표현형은 역상형광현미경 및 면역염색법을 통해 분석했다. 본 연구를 통하여 서로 다른 세포외 기질 물질이 세포의 부착 및 성장 속도에 영향을 미치며, 심근세포의 특이성을 나타내는 단백질의 형성에도 차이를 보이는 것을 확인했다.

• 한국자기학회지
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• 제18권1호
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• pp.14-18
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• 2008

본 연구에서는 Bi:YIG($Bi_{0.5}Y_{2.5}Fe_5O_{12}$) 막을 에어로졸 성막법을 이용하여 제작함에 있어서, 에어로졸을 구성하는 수송가스의 유량이 막의 자기적 특성과 광학적인 특성에 대하여 분석하였다. 직경 $100{\sim}500$ nm 의 Bi:YIG 분말을 질소 가스를 수송가스로 사용하여 성막을 실시하였고, 이 때, 수송가스의 유량은 0.5 l/min${\sim}10$ l/min 사이에서 변화시켰다. 수송가스의 유량이 증가할수록 Bi:YIG 막의 보자력은 51 Oe에서 37 Oe까지 지수함수적으로 감소하였다. 이것은 충돌에너지가 증가함에 따라 막내부 혹은 막표면의 결함이 감소하였기 때문이라고 고찰되었다. 포화자화는 유량이 증가할수록 감소하였는데, 이는 충돌에너지가 강해짐에 따라 결정이 왜곡되는 힘을 받았기 때문이라고 고찰되었다.