• 한국재료학회지
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• 제18권1호
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• pp.38-44
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• 2008

The micro-structural changes, strength characteristics, and micro-fractural behaviors at the joint interface between a Sn-4.0wt%Ag-0.5wt%Cu solder ball and UBM treated by isothermal aging are reported. From the reflow process for the joint interface, a small amount of intermetallic compound was formed. With an increase in the isothermal aging time, the type and amount of the intermetallic compound changed. The interface without an isothermal treatment showed a ductile fracture. However, with an increase in the aging time, a brittle fracture occurred on the interface due mainly to the increase in the size of the intermetallic compounds and voids. As a result, a drastic degradation in the shear strength was observed. From a microshear test by a scanning electron microscope, the generation of micro-cracks was initiated from the voids at the joint interface. They propagated along the same interface, resulting in coalescence with neighboring cracks into larger cracks. With an increase in the aging time, the generation of the micro-structural cracks was enhanced and the degree of propagation also accelerated.

• Coupled systems mechanics
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• 제8권1호
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• pp.71-93
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• 2019

Finite element simulations of solid mechanics problems often involve the use of Non-Confirming Meshes (NCM) to increase accuracy in capturing nonlinear behavior, including damage and plasticity, in part of a solid domain without an undue increase in computational costs. In the presence of material nonlinearity and plasticity, higher-order variables are often needed to capture nonlinear behavior and material history on non-conforming interfaces. The most popular formulations for coupling non-conforming meshes are dual methods that involve the interpolation of a traction field on the interface. These methods are subject to the Ladyzhenskaya-Babuska-Brezzi (LBB) stability condition, and are therefore limited in their implementation with the higher-order elements needed to capture nonlinear material behavior. Alternatively, the enriched discontinuous Galerkin approach (EDGA) (Haikal and Hjelmstad 2010) is a primal method that provides higher order kinematic fields on the interface, and in which interface tractions are computed from local finite element estimates, therefore facilitating its implementation with nonlinear material models. The inclusion of higher-order interface variables, however, presents the issue of preserving material history at integration points when a increase in integration order is needed. In this study, the enriched discontinuous Galerkin approach (EDGA) is extended to the case of small-deformation plasticity. An interface-driven Gauss-Kronrod integration rule is proposed to enable adaptive enrichment on the interface while preserving history-dependent material data at existing integration points. The method is implemented using classical J2 plasticity theory as well as the pressure-dependent Drucker-Prager material model. We show that an efficient treatment of interface variables can improve algorithmic performance and provide a consistent approach for coupling non-conforming meshes in inelasticity.

• BMB Reports
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• 제52권6호
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• pp.379-384
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• 2019

Epithelial-mesenchymal transition (EMT) is widely-considered to be a modulating factor of anoikis and cancer metastasis. We found that, in MDA-MB-231 cells, TP53I11 (tumor protein P53 inducible protein 11) suppressed EMT and migration in vitro, and inhibited metastasis in vivo. Our findings showed that hypoxic treatment upregulated the expression of $HIF1{\alpha}$, but reduced TP53I11 protein levels and TP53I11 overexpression reduced $HIF1{\alpha}$ expression under normal culture and hypoxicconditions, and in xenografts of MDA-MB-231 cells. Considering $HIF1{\alpha}$ is a master regulator of the hypoxic response and that hypoxia is a crucial trigger of cancer metastasis, our study suggests that TP53I11 may suppress EMT and metastasis by reducing $HIF1{\alpha}$ protein levels in breast cancer cells.

• 접착 및 계면
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• 제18권3호
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• pp.118-126
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• 2017

천연섬유강화 복합재료에서 여러 가지 섬유표면 개질을 통해서 천연섬유와 고분자매트릭스 사이에 계면접착과 복합재료 특성을 향상시키고자 하는 많은 연구 노력이 있었다. 본 연구에서는 폐양모섬유 강화 폴리프로필렌 매트릭스 복합재료를 압축성형공정 방법으로 제조하였고, 그들의 기계적 특성 및 충격 특성을 분석하였다. 그 결과, 폐양모/폴리프로필렌 복합재료의 인장 및 굴곡 특성 그리고 충격강도는 수산화나트륨(NaOH)을 이용한 알칼리처리와 3-glycidylpropylsilane(GPS)을 이용한 실란처리와 같은 처리매체에 크게 의존하였다. 실란처리를 한 폐양모섬유를 포함한 복합재료는 알칼리처리를 한 폐양모섬유를 포함한 것보다 더 우수한 기계적 특성과 충격저항성을 나타내었다. 복합재료 파단면은 특성 증가가 폐양모섬유와 폴리프로필렌 매트릭스 사이에 계면결합의 향상에 의한 것임을 정성적으로 뒷받침해주었다.

• 대한치과보철학회지
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• 제25권1호
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• pp.95-118
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• 1987

This study was undertaken to observe the elemental transition of Interface depending on different pretreatment methods, the number of filings, the kinds of porcelain powders and the various alloys in ceramo-metal restoration. The materials used in this study were Pors-on $4^{(R)}$ and Ceramco porcelain powder to compare the differences depending on the pretreatement methods and the number of firings. Ceramco porcelain powder and Vita porcelain powder were used to compare the differences of elemental transition depending on the porcelain powders. The $Parasil^{(R)},\;PGV^{(R)}$ and Pors-on $4^{(R)}$ as Pd-Ag alloy were used to compare the difference of elemental transition depending on the various alloys. The pretreatment methods were : no treatment, treatment under vacuum and air, treatment with 50 % hydrofluoric acid and double heat tretament. The number of firings were 3, 5 and 7 repeated firings All specimens were observed by SEM and concentration of elements were analyzed quantitatively with EPMA The results of this study were obtained as follows : 1. In the groups of air-treatment, concentration of Sn were the highest and widest. A high concentration of In were in the groups of vacuum and air treatment. 2. There were no significant differences in concentration of Sn between the group of vacuum, 5 minutes hydrofluoric acid and double heat treatment. (p>0.05) 3. As the period of time of hydrofluoric acid treatment increased, not only were the trace elements reduced but the main components such as Pd and Ag were also reduced. 4. Concentration of Sn and In increased and diffused with repeated firings but 5 repeated and 7 repeated firings groups had no significant differences. (p>0.05) 5. Sn were more concentrated in the group of Ceramco porcelaion powder than Vita porcelain powder. 6. The higher concentration of trace elements in the alloy, the more increasing concentration of Sn and In in the interface.

• 접착 및 계면
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• 제17권3호
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• pp.96-103
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• 2016

본 연구에서는 셀룰로스계 천연섬유인 대나무와 poly(lactic acid) (PLA)로 구성된 펠렛을 압출공정으로 제조하고, 여러 가지 함량의 대나무섬유/PLA 바이오복합재료를 사출공정을 통해 성형하였다. 바이오복합재료의 굴곡, 인장, 충격 특성 및 열변형온도에 미치는 대나무섬유의 수처리 영향을 조사하였다. 천연섬유의 열안정성, 바이오복합재료의 굴곡특성, 인장탄성률 및 충격특성은 섬유 함량은 물론 수처리 유 무에 의존한 반면, 열변형온도는 주로 수처리에 의해 영향을 받았다. 바이오복합재료의 기계적 특성과 충격특성의 증가는 이를 구성하고 있는 대나무섬유와 PLA 매트릭스 사이의 계면결합력이 대나무섬유의 수처리에 의해 향상되었기 때문이다. 연구결과는 친환경적이고 작업친화적인 물을 이용한 천연섬유의 전처리가 바이오복합재료의 성능을 향상시키는데 기여할 수 있다는 것을 제시하여 준다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2000년도 추계학술대회 및 발표대회 강연 및 발표논문 초록집
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• pp.43-43
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• 2000

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1994년도 춘계학술대회강연 및 발표대회 강연및 발표논문 초록집
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• pp.21-21
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• 1994

• 접착 및 계면
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• 제2권3호
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• pp.1-8
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• 2001

${\gamma}$-APS (${\gamma}$-aminopropyltriethoxysilane)로 표면처리된 천연제올라이트와 에폭시 수지 복합 재료의 표면 자유 에너지, 인상강도 및 계면 모폴로지에 대해 연구하였다. 표면처리하지 천연제올라이트의 표면 자유에너지 성분 중에서 무극성 성분인 Lifshitz-van der Waals 성분, ${\gamma}{\frac{LW}{SV}}$는 $19.22mJ/m^2$이었고, 극성 성분인 Lewis acid-base 성분, ${\gamma}{\frac{AB}{SV}}$는 $15.27mJ/m^2$이 있다. ${\gamma}$-APS의 처리농도가 증가함에 따라 ${\gamma}{\frac{LW}{SV}}$값은 증가하였지만 ${\gamma}{\frac{AB}{SV}}$는 감소하였으며, 이는 ${\gamma}$-APS의 소수성 성분인 알킬기의 영향이 친수성 기인 아민이나 수산기의 영향보다 커지기 때문이다. 인장강도와 Young율은 ${\gamma}$-APS 처리에 의해 개선되었으며, SEM 분석에 의해 계면특성이 향상되었음을 확인하였다.

• 대한치과보철학회지
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• 제29권3호
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• pp.1-32
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• 1991

Tho osseointegrated dental prosthetic treatment has develped for the edentulous patient with severely resorbed alveolar ridge, and has given us a successful clinical results to date. Nowadays the partially edentulism is included among the indications of the osseointegrated prosthetic treatment. The purpose of this study was to analyze the stress distribution at supporting bone according to the types of connection modality between implant and tooth in the superstructure. Two dimensional finite element stress analysis was applied for this study. FEM models were created using software Super SAP for MBM 16bit personal computer. Three modalities of connection were modeled and analyzed under load condition. The results were as follws: 1. The stress develped at tooth and implant in the cancellous bone was lower in the case of rigid connection than in the case of norigid connection, but higher between the two implants in the case of rigid connection than in the case of nonrigid connection. 2. The stress developed at the cortical bone and at the supporting bone interface was lower in the case of rigid connection than in the case of nonrigid connection 3. The stress developed at the supporting tissue interface of the implant nearby the tooth, was lower in the case of rigid connection than in the case of nonrigid connection. 4. The stress developed at the supporting tissue interface of posteriormost implant, was same between the cases of rigid and nonrigid connection. 5. The stress distribution related to the freestanding case was generally similar to the stress distribution pattern of nonrigid connection case. 6. The magnitude of applied load which produces deformation within elastic limit, had influence on the absolute value of stress, but had no influence on the pattern of stress distribution of the same case.