This study proposes flexural failure design criteria of continuous slabs enhanced by a hybrid system of fiber reinforced polymer (FRP) and ultra high performance concrete (UHPC). The proposed hybrid retrofit system is designed to be placed at the top surface of the slabs for flexural strengthening of the sections in both positive and negative moment zones. The enhancing mechanisms of the proposed system for both positive and negative moment regions are presented. The neutral axis of the enhanced sections in positive moment zone at flexural failure is enforced to be in UHPC overlay for preventing the compression in FRP. From this condition, a relationship between design parameters of FRP and UHPC is established. Although the capacity of the proposed retrofit system to enhance flexural strength and ductility is confirmed through experiments of one-way RC slabs having two continuous spans, the retrofitted slabs failed in shear. To prevent this shear failure, a design criteria of flexural failure is proposed.

본 연구는 대기오염으로 인한 SO2와 NO2 그리고 산성비 등의 건성 및 습성강하물의 영향을 받고 있는 공단지역 주변 산림과 대조지역의 해송림에서 해송림의 쇠퇴도 사이에 상관분석과 단계적 회귀분석을 통하여 해송 잎의 쇠퇴와 엽록소 함량에 가장 영향을 미치는 인자를 구명하였다. 수관통과우의 pH는 도시공단지역이 봄철 4.65, 가을철 4.72이었고, 대조지역이 봄철 5.32과 가을철 5.34였다. 음이온 성분 중에서 NO3-의 농도는 도시공단지역이 52.13 ㎎/ℓ, 대조지역은 37.85 ㎎/ℓ이었다. SO42- 함량은 도시공단지역이 57.89 ㎎/ℓ, 대조지역이 36.21 ㎎/ℓ이었다. Ca2+의 농도는 도시공단지역이 27.27 ㎎/ℓ, 대조지역이 9.48 ㎎/ℓ이었다. 해송 잎의 엽록소 a의 함량은 도시공단지역이 0.2378이었고, 대조지역은 0.4378이었다. 해송의 쇠퇴도는 도시공단지역 2.97, 대조지역 1.20이었다. 해송 임분의 쇠퇴도와 강우의 이온성분, SO2, NO2 농도와 상관분석 결과에서 강우산도 상호간에는 부의 상관(r=-0.8672)이었고, 대기 중 SO2 농도는 정의 상관(r=0.8924)이었으며, NO2 농도도 정의 상관(r=0.8428)이었다. 이러한 산성강하물 상호간의 상관관계는 pH(r=-0.8672), NO3-(r=0.6996), SO42-(r=0.8497), SO2 (r=0.8924), NO2(r=0.8428)는 1% 수준에서 상관이 있었다.

An attempt was made to evaluate creep reliability of two commercial Ni-based superalloys by using ultrasonic wave. The materials include fine-grained PM alloy fabricated by mechanical alloying and subsequent hot isostatic pressing, and IN738LC cast alloy with a grain size of a few cm. Microstructural parameters (fraction of creep cavity and size of precipitates) and ultrasonic parameters (velocity, attenuation) were measured to try to find relationships between them. Ultrasonic velocity decreased with creep cavity formation in PM alloy. On the other hand, no distinct changing trend of ultrasonic velocity was observed for IN738LC alloy. Ultrasonic attenuation was found to have a linear correlation with the size of precipitates and was suggested as a potential parameter for monitoring creep reliability of IN738LC alloy.

was successfully formed on a Ti specimen by MAO (Micro-Arc-Oxidation) method treated in electrolyte. This study deals with the influence of voltage and working time on the change of surface microstructure and phase composition. Voltage affected the forming rate of the oxidized layer and surface microstructure where, a low voltage led to a high surface roughness, more holes and a thin oxidized layer. On the other hand, a high voltage led to more dense surface structure, wider surface holes, a thick layer and fewer holes. Higher voltage increases photocatalytic activity because of better crystallization of the oxidized layer and good phase composition with anatase and rutile , which is able to effectively separate excited electrons and holes at the surface.

Ameloblastomas are benign odontogenic tumor and the most common neoplasm in jaws and they have locally invasive property and high recurrence rate. Four typical subtypes ameloblastomas are plexiform, follicular, granular cell and acanthomatous type, but their developmental states during tumorigenesis are uncertain. And thus authors studied about developing states of four types of ameloblastomas by immunohistochemical staining for cytokeratin 8/18 which was an intermediate filament of epithelial cell origin and for vimentin which was an intermediate filament of mesenchymal cell origin, and then by comparative analyses of the results. Authors selected seven cases for every four types of ameloblastomas, and then performed immunohistochemcial staining for cytkeratin 8/18 and vimentin to all selected specimen by using monoclonal antibodies about cytoleratin 8/18 and vimentin, LSAB(Labelled StreptoAvidin Biotin) reactant and HRP(Horse Radish Peroxidase) system. Labelling indices of cytokeratin 8/18 of plexiform and follicular types of ameloblastomas were significantly high values in the group of ameloblast-like cells and labelling indices of cytokeratin 8/18 of all types of ameloblastoma were high values in the group of transformed cells, but their differences were not significant. Labelling index of vimentin of plexiform ameloblastoma was significantly high value in the group of ameloblast-like cells and others showed comparatively lower values. Labelling index of vimentin of granular cell type of ameloblastoma in the group of transformed cells was significantly high value and others showed comparatively lower values. Consequently the most primitive form of ameloblastoma was plexiform, and more differenciated form was follicular type and granular cell type and acanthomatous type were most differenciated form of ameloblastomas

This study proposes a hybrid system of fiber reinforced polymer (FRP) and ultra high performance concrete (UHPC) to enhance flexural strength of existing reinforced concrete (RC) slabs. The proposed system is designed to be placed at the top surface of the slabs for flexural strengthening of the sections in both positive and negative moment zones. The enhancing mechanisms of the proposed system for both positive and negative moment regions are presented. Moreover, to prevent the compression in FRP of the enhanced sections in positive moment zone at flexural failure, neutral axis of the sections at failure is enforced to be in UHPC overlay. From this condition, a relationship between design parameters of FRP and UHPC is established.