• Applied Microscopy
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• 제42권1호
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• pp.17-26
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• 2012

배회성거미류의 배후발생과정에서 형태적 분화가 행동학적 특성으로 발현되는 기전을 규명하기 위하여 광릉늑대거미(Arctosa kwangreungensis) 후기배아와 각 발생 단계의 유충을 실험재료로 그 조직학적 및 미세구조적 변화를 광학 및 주사전자현미경으로 분석하였다. 난황주머니를 가진 후기배아는 부속지의 근육조직과 신경절의 미분화로 비활성상태를 유지하며, 시각기의 신경절과 신경의 발달도 미약하였다. 제1령 유충의 두흉부에서는 미분화된 세포집단이 관찰되고 체색의 발현과 복부신경절의 분화가 현저하였다. 먹이 활동을 시작하는 제2령 유충의 중추신경계에는 신경섬유가 급격히 증가되었고, 성체와 유사한 부속지의 분절구조와 시각기의 조직학적 체제가 확립되었다. 제3령 이후의 유충들은 탈피를 거듭하여 두흉부에서 중추신경계가 차지하는 영역이 축소되었고 독선과 근육조직, 그리고 결합조직등의 활발한 분화가 진행되었다. 먹이활동을 시작하는 제2령 유충 단계에서 부속지와 시각기의 조직학적 발생과 이를 통제하는 신경계의 분화가 완료되는 것으로 미루어, 섭식환경이 배후발생과정을 조절할 수 있으며, 특히 시각과 부속지에 의존하여 먹이를 포획하는 배회성거미류의 행동 습성이 형태조직학적 분화와 연관되어 있음을 확인할 수 있었다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2002년도 추계학술강연 및 발표대회
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• pp.39-40
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• 2002

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2002년도 추계총회 및 연구발표회 초록집
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• pp.44.1-44
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• 2002

• 한국재료학회:학술대회논문집
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• 한국재료학회 1997년도 한국재료학회 춘계학술발표회
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• pp.85-85
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• 1997

• 한국재료학회:학술대회논문집
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• 한국재료학회 1998년도 IUMRS-ICEM ABSTRACT BOOK
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• pp.140.1-140
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• 1998

• 대한금속재료학회지
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• 제48권10호
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• pp.914-921
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• 2010

Studies were carried out to assess the microstructural and mechanical properties of ferriticmartensitic steel under a flowing sodium environment. HT9 (12Cr-MoVW) and Gr.92 (9Cr-MoVNbW) steel were exposed to liquid sodium at $650^{\circ}C$ containing dissolved oxygen of 20 ppm for 2333 hours and evaluations of the microstructure as well as the mechanical properties of the microhardness and nanoindentation were carried out. The result showed that both HT9 and Gr.92 exhibited macroscopic weight loss caused by general corrosion as well as localized types such as intergranular corrosion and pitting. Decarburization at the steel surface took place as the test proceeded. As the Cr content increased, dissolution and decarburization were suppressed. Assessment of the actual cladding geometry revealed that an aging process rather than decarburization governed the mechanical properties, which resulted in a decrease of the microhardness and yield stress.

• 한국세라믹학회지
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• 제38권5호
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• pp.405-411
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• 2001

Compacts of a mixture of fine $\alpha$-Si$_3$N$_4$powders, 6% $Y_2$O$_3$and 1% $Al_2$O$_3$were attrition milled time on phase and microstructural development in silicon nitride ceramics. The sintered surface and the interior showed different behaviors in phase and microstructral developments. Increased oxygen content with increased milling time of powder mixture leads to the formation of Si$_2$$N_2$O phase at temperatures as low as 155$0^{\circ}C$. Si$_2$$N_2$O is stable in the interior of the samples but unstable in the surface region of the specimen sintered at higher temperature. This results in a duplex structure where the interior consists of Si$_2$$N_2$O grains dispersed in $\beta$-Si$_3$N$_4$matrix and a surface which contains only $\beta$-Si$_3$N$_4$. The alpha to beta phase transformation and the microstructural development are shown to be influenced by the formation and decomposition of the Si$_2$$N_2$O.

• 열처리공학회지
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• 제32권6호
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• pp.256-262
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• 2019

The microstructural features and texture development by both hot rolling and hot forging in ${\gamma}-TiAl$ alloy were investigated. In addition, additional heat treatment after hot forging was conducted to recognize change of the microstructure and texture evolution. The obtained microstructural features through dynamic recrystallization after hot deformed ${\gamma}-TiAl$ were quite different because two kinds of formation process were occurred depending on deformation condition. However, analyzed texture tends to be random orientation due to intermediate annealing up to ${\alpha}+{\beta}$ region during the hot deformation process. After additional heat treatment, microstructure transformed into fully lamellar microstructure and randomly oriented texture was also observed due to the same reason as before. Tensile test at room temperature demonstrated that anisotropy of mechanical properties were not appeared and transgranular fracture was occurred between interface of ${\alpha}_2/{\gamma}$. As a result, it could be suggested that microstructural features influenced much more than texture development on mechanical properties at room temperature.

• 터널과지하공간
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• 제25권5호
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• pp.435-449
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• 2015

풍촌석회암과 막골석회암을 대상으로 $-18{\sim}+32^{\circ}C$의 온도범위에서 총 50회의 인공적인 동결-융해 풍화시험을 수행하고 그로 인한 물리적 성질과 미세구조의 변화를 정량적으로 분석하였다. 두 가지 암종 모두 건조무게와 P,S파 속도는 지속적으로 감소하는 경향을 보였고, 흡수율은 증가하는 경향을 보였다. X선 단층촬영 영상분석 결과 실험 후 공극률이 증가하였으며, 공극부피, 등가직경, 국부두께, 방향성 등 여러 지표에서 공극의 생성 및 확장을 확인할 수 있었다. 막골석회암의 물리적 미세구조적 변화가 풍촌석회암에 비해 크게 나타났는데 이는 초기 상태의 막골석회암이 더 많은 공극과 미세균열을 가지고 있었기 때문으로 추정된다. 본 연구는 암석의 물리적 성질과 미세구조적 성질을 통합적으로 분석함으로써 향후 암석의 풍화 연구에 적용될 수 있을 뿐만 아니라, 저온지역의 건설, 자원개발 활동에 기초자료로써 이용될 것으로 기대된다.

• International Journal of Concrete Structures and Materials
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• 제8권4호
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• pp.289-299
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• 2014

Alkali-activated slag concretes are being extensively researched because of its potential sustainability-related benefits. For such concretes to be implemented in large scale concrete applications such as infrastructural and building elements, it is essential to understand its early and long-term performance characteristics vis-a'-vis conventional ordinary portland cement (OPC) based concretes. This paper presents a comprehensive study of the property and performance features including early-age isothermal calorimetric response, compressive strength development with time, microstructural features such as the pore volume and representative pore size, and accelerated chloride transport resistance of OPC and alkali-activated binder systems. Slag mixtures activated using sodium silicate solution ($SiO_2$-to-$Na_2O$ ratio or $M_s$ of 1-2) to provide a total alkalinity of 0.05 ($Na_2O$-to-binder ratio) are compared with OPC mixtures with and without partial cement replacement with Class F fly ash (20 % by mass) or silica fume (6 % by mass). Major similarities are noted between these binder systems for: (1) calorimetric response with respect to the presence of features even though the locations and peaks vary based on $M_s$, (2) compressive strength and its development, (3) total porosity and pore size, and (4) rapid chloride permeability and non-steady state migration coefficients. Moreover, electrical impedance based circuit models are used to bring out the microstructural features (resistance of the connected pores, and capacitances of the solid phase and pore-solid interface) that are similar in conventional OPC and alkali-activated slag concretes. This study thus demonstrates that performance-equivalent alkali-activated slag systems that are more sustainable from energy and environmental standpoints can be proportioned.