• 대한소아치과학회지
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• 제23권2호
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• pp.559-574
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• 1996

The purpose of this study was to determine whether there was any correlation between temporomandibular joint dysfunction and structure of the mandibular condyle. Weanling rats had their masseter muscles resected and immunohistochemical findings were observed with a light microscope. The results obtained were as follows : 1. The condylar cartilage region was divided into articular, proliferating, cartilage cell and hypertrophic cell layers according to cell morphology. 2. In light microscopic views, the proliferating and cartilage cell layers of the experimental group decreased gradually and at the 8th week significantly. 3. In immunohistochemical staining for type I and II collagen, a reaction was detected in the lower part of proliferating cell and cartilage cell layers. In the cartilage cell layers, a stronger cellular reaction was present. Immunohistochemical staining for type II collagen reacted more strongly than that of type I collagen. 4. In immunohistochemical staining for proteoglycan, the staining of the experimental group resembled the control group and gradually showed a weak reaction. The proliferating and cartilage cell layers reacted more strongly than the hypertrophic cell layer. 5. In immunohistochemical staining for proliferating cell nuclear antigen(PCNA), the strong reaction was detected in the nucleus of the proliferating cell layer both in control and experimental groups. But the thickness of the proliferating layer decreased in experimental group, consequently the reaction of the experimental group was reduced more than that of the control group.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.95-95
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• 2009

Zinc coatings provide the most effective and economical way of protecting steel against corrosion. There are three types of galvanizing lines typically used in production line in galvanizing industries,Galvanize (GI) coating (Zn-0.1-0.3%Al), Galfan coating (Zn-5%Al), Galvalume(GL) coating (45%Zn-Al). In continuous Galvanizing lines, the immersed bath hardware (e.g. bearings, sink, stabilizer, and corrector rolls, and also support roll arms and snout tip) are subjected to corrosion and wear failure. Understanding the reaction of these materials with the molten Zn alloy is becomes scientific and commercial interest. To investigate the reaction with molten Zn alloys, static immersion test performed for 4, 8, 16, and 24 Hr. Two different baths used for the static immersion, which are molten Zn and molten Zn-55%Al. Microstructures characterization of each of the materials and intermetallic layer formed in the reaction zone was performed using optical microscope, SEM and EDS. The thickness of the reaction layer is examined using image analysis to determine the kinetics of the reaction. The phase dominated by two distinct phase which are eutectic carbide and matrix. The morphology of the intermetallic phase formed by molten Zn is discrete phase showing high dissolution of the material, and the intermetallic phase formed by Zn-55wt%Al is continuous. Aluminum reacts readily with the materials compare to Zinc, forming iron aluminide intermetallic layer ($Fe_2Al_5$) at the interface and leaving zinc behind.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.976-979
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• 2002

This research presents the new method to fabricate small features through applying chemical mechanical micro machining(C3M) for Al5052 and single crystal silicon. To improve machinability of ductile and brittle material, reacted layer was formed on the surface before micro-drilling process by chemical reaction with $HNO_3$(10wt%) and KOH(10wt%). And then workpieces were machined to compare conventional micro-drilling process with newly suggested one. To evaluate whether or not the machinability was improved by the effect of chemical condition, surface defects such as burr, chipping and crack generation were measured. Finally, it is confirmed that C3M is one of the feasible tools for micro machining with the aid of effect of the chemical reaction.

• 한국세라믹학회지
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• 제30권11호
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• pp.949-954
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• 1993

Microstructural development at the ZrO2/NiTi bonding interface and reaction products were examined and identified with SEM and AEM. Ti-oxide, Ti2Ni and Ni2Ti layer were observed whose thickness depends on bonding temperature typically. The development of Ti-oxide layer is related with oxygen ion in ZrO2 and liquid phase Ti2Ni. It is considered that compositional deviation from homogeneity and residual stress caused by thermal expansion mismatch are closely related with the formation of the Ti2Ni phase.

• 소성∙가공
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• 제7권5호
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• pp.481-488
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• 1998

The active metal brazing was applied to bond Alumina and Ni-Cr steel by Ag-Cu-Zr-Sn alloy and the interfacial microstructure and reaction mechanism were investigated. Polycrystalline monoclinic $ZrO_2$ with a very fine grain of 100-150 nm formed at the alumina grain boundary contacted with Zr segregation layer at the interface. The $ZrO_2$ layer containing the inclusions and cracks were developed at the boundary of inclusion/$ZrO_2$ due to the difference in specific volume. The development of $ZrO_2$ at the interface was successfully explained by the preferential penetration of $ZrO_2$ at the interface was successfully explained by the preferential penetration of Zr atoms a higher concentration of oxygen and a high diffusion rate of Al ions into molten brazing alloy.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.823-829
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• 2000

[ $Nb/MoSi_2$ ]laminate composites have been successfully fabricated by hot pressing in a graphite mould. Lamination of Nb foil and $MoSi_2$ layer showed a sufficient improvement in the absorbed impact energy compared to that of monolithic $MoSi_2$ material. The impact value of $Nb/MoSi_2$ laminate composites obviously is reduced when sintered at temperatures higher than 1523K, even if the composite density contributing to impact load increased along with fabricating temperatures. Impact value of laminate composites was also drastically decreased with the growth of reaction layer after the heat treatment. However, it was effective to increase the pressure at the same sintering temperature for the improvement of the impact value.

• Applied Microscopy
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• 제14권2호
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• pp.15-28
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• 1984

The endosperm cells and the umbiliform layer of ginseng (Panax ginseng C.A. Meyer) seed are studied with light and electron microscope. Differentiated mitochondria, ER cisternae, proplastids and ribosomes are characteristically observed in the endosperm cells of matured seed. The cell inclusions contain the protein bodies and the spherosomes. Protein body contains, in proteinaceous matrix, globoids and crystalloids. Particularly the crystalloids have the lattice structure, and the formation of globoids is closely related with ER. Umbiliform layer has the positive reaction on alcian blue (pH 2.5) and the metachromasis on the toluidine blue. The umbiliform layer is formed by autolysis of endosperm cells, and composed of the deformated cell wall and the lipoprotein bodies. Particularly a part of the lipoprotein body and the fibrilar network structure have the positive reaction on acid phosphatase.

• 한국분말재료학회지
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• 제27권1호
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• pp.63-71
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• 2020

It is necessary to fabricate uniformly dispersed nanoscale catalyst materials with high activity and long-term stability for polymer electrolyte membrane fuel cells with excellent electrochemical characteristics of the oxygen reduction reaction and hydrogen oxidation reaction. Platinum is known as the best noble metal catalyst for polymer electrolyte membrane fuel cells because of its excellent catalytic activity. However, given that Pt is expensive, considerable efforts have been made to reduce the amount of Pt loading for both anode and cathode catalysts. Meanwhile, the atomic layer deposition (ALD) method shows excellent uniformity and precise particle size controllability over the three-dimensional structure. The research progress on noble metal ALD, such as Pt, Ru, Pd, and various metal alloys, is presented in this review. ALD technology enables the development of polymer electrolyte membrane fuel cells with excellent reactivity and durability.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.469-474
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• 2002

Laser and hot air reflow soldering of PBGA solder ball was investigated. Experimental results showed that surface quality and shear strength of solder bumps reflowed by laser was superior than the solder bumps reflowed by hot air, and the microstructure inside the solder bumps reflowed by laser was much finer. Analysis on interfacial reaction showed that eutectic solder reacted with Au/Ni/Cu pad shortly after the solder was melted. Interface of solder bump reflowed by laser consists of a continuous AuSn$_4$ layer and remnant Au element. Needle-like AuSn$_4$ grew sidewise from interface, and then spread out to the entire interface region. A thin layer of Ni$_3$Sn$_4$ intermetallic compound was found at the interface of solder bump reflowed by hot air, AuSn$_4$ particles distributed inside the whole solder bump randomly. It is the combination effect of the continuous AuSn$_4$ layer and finer eutectic microstructure inside the solder bump reflowed by laser that resulted in higher shear strength.

• 한국정밀공학회지
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• 제2권3호
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• pp.41-46
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• 1985

The behavior of the burn-on in sand mold has been investigated by varying the pouring metal, bonding materials, additive materials and molding sand. The results obtained from thease experiments are as follows; 1) The burn-on layer of silica sand decreased in order of carbon steel, gray cast iron and stainless steel, and thease burn layer proceeded mostly by producing FeO. 2) The burning reaction of silica sand mold in carbon steel castings declined with increasingly bentonite content, but water-glass scarcely took part in the burn-on reaction. 3) The addition of feldspar and seacoal to silica sand promoted the inhibiting burn-on. 4) The burn-on layer of sand mold decreased of silica sand, chromite sand and olivine sand.