• Restorative Dentistry and Endodontics
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• v.35 no.6
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• pp.445-452
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• 2010

Objectives: The aim of this study was to compare apical sealing ability and physical properties of MTA, MTA - AH-plus mixture (AMTA) and experimental Portland cement - Epoxy resin mixture (EPPC) for a development of a novel retro-filling material. Materials and Methods: Forty-nine extracted roots were instrumented and filled with gutta-percha. Apical root was resected at 3 mm and the retro-filling cavity was prepared for 3 mm depth. Roots were randomly divided into 3 groups of 15 roots each. The retro-filling was done using MTA, AMTA, and EPPC as the groups divided. Four roots were used as control groups. After setting in humid condition for 24 hours, the roots were immersed in 1% methylene blue dye solution for 72 hours to test the apical leakage. After immersion, the roots were vertically sectioned and photos were taken to evaluate microleakage. Setting times were measured with Vicat apparatus and digital radiographs were taken to evaluate aluminum equivalent thickness using aluminum step wedge. The results of microleakage and setting time were compared between groups using one-way ANOVA and Scheffe's post-hoc comparison at the significance level of 95%. Results: AMTA and EPPC showed less microleakage than MTA group (p < 0.05). AMTA showed the highest radio-opacity than other groups and the novel EPPC showed 5 mm aluminum thickness radio-opacity. EPPC showed the shortest initial and final setting times than other groups while the MTA showed the longest (p < 0.05). Conclusions: Under the condition of this study, the novel composite using Portland cement-Epoxy resin mixture may useful for retro-filling with the properties of favorable leakage resistance, radio-opacity and short setting time.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.537-549
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• 1999

선형탄성 파괴해석은 균열을 갖는 변형률 경화재료의 파괴거동을 예측하는데 불충분하기 때문에 최근에는 균열 선단 부에서 대규모 소성 역을 갖는 균열 체에 적용할 수 있는 많은 파괴역학개념이 제안되고 있다. 따라서, 본 연구에서는 대규모항복 조건하의 연성파괴를 보이는 평판을 정확하게 해석할 수 있는 새로운 유한요소모델을 제시하고자 한다. 균열 선단 부의 응력 장을 정의하는데 가장 지배적인 파괴매개변수인 J-적분 값과 소성 역의 크기 및 형상을 J-적분법과 등가영역적분법을 통해 파괴거동을 설명할 수 있도록 증분소성이론에 기초를 둔 p-version 유한요소해석이 채택되었다. 제안된 유한요소모델에 의한 수치해석결과는 이론 해와 h-version 유한요소해석과 비교되었다.

• 대한생식의학회:학술대회논문집
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• 2007.06a
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• pp.121-121
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• 2007

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1183-1192
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• 1989

본 논문에서는 평면변형률 상태하에서 안정하게 성장하는 균열선단에 집중 되어있는 강소성역의 해석에 역점을 두어 재결정법과 탄.소성유한요소법을 도입하여 안정 성장균열 선단에 형성되는 균열 성장저항에 직접적인 영향을 미치고 있는 소성 역의 크기나 형태에 대한 실험 및 해석을 하였다.

• Journal of the Korean Society of Radiology
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• v.83 no.1
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• pp.28-41
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• 2022

Acute coronary syndrome involves three types of coronary artery disease associated with sudden rupture of coronary artery plaque, and has a clinical presentation ranging from ST-segment elevation myocardial infarction (STEMI) to non-ST-segment elevation myocardial infarction (NSTEMI) or unstable angina. Cardiac CT can help quantify and characterize atherosclerotic plaques. According to a previous study, low-attenuation plaque, napkin ring sign, positive remodeling, spotty calcification, and increased perivascular fat attenuation are associated with plaque ruptures on cardiac CT. Therefore, coronary artery stenosis, as well as acute coronary artery syndrome, can be diagnosed using cardiac CT.

• Journal of the KSME
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• v.50 no.8
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• pp.41-45
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• 2010

동맥에서의 맥파전달 속도는 동맥 혈류와 혈관벽의 상호작용에서 유발되며, 동맥경화, 당뇨합병증 등의 진단 등에 널리 사용되고 있다. 증가된 맥파전달속도는 혈관 노화 및 여러 병리학적 상황과 연관된 것으로 보고되고 있다. 따라서 이 글에서는 이러한 동맥 맥파전달속도의 생체유체역학적 발생 기전 및 의학적 중요성에 대하여 논의하며, PWV진단의 문제점 및 향후 발전방향에 대해서도 기술한다.

• 대한생식의학회:학술대회논문집
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• 2004.11a
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• pp.64-64
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• 2004

• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.61-68
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• 2007

The problem on cyclic plate load tests was analyzed by finite element method using an anisotropic hardening constitutive model. The constitutive model was coded to user subroutine in ABAQUS. Using the result of the analysis, Young's moduli corresponding to various strain levels were evaluated by a back calculation method and were very similar to those of input. On the basis of the back calculation method plate loading tests were verified. As a result, deformation moduli could be evaluated practically from cyclic plate load tests with respect site conditions.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.534-540
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• 2004

Packable resins have been introduced in the market with high expectations as an alternative to amalgam. They are characterized by a high-filler load and a filler distribution that gives them a different consistency compared with the hybrid resins. The effect of high filler load on the microhardness and polymerization shrinkage of packable resins was tested. Hybrid resins were also tested to compared with the packable resins. As a result, packable resins showed a much greater microhardness value than hybrid resins. All the tested resins have a correlationship with the microhardness and filler content (vol%). The packable resins showed much less polymerization shrinkage than hybrid resins. The filler content and polymerization shrinkage were inversely correlated in the tested resins.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.229-235
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• 1989

The influence of monogalvanized layer to fatigue strength of two different mating metal specimens (HS*GA, HS*GAB) of high strength steels(HS) and of monogalvanized steel sheets(GA, GAB) were investigated under tensile-shear repeated load, and hardness test. Some of the results are; (1) The main cause of crack initiation and growth at high load range is plastic bending hinge. (2) In low load range, the cracks initiated near the nugget front where the hardness variation is steep.