• 한국재료학회지
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• 제26권1호
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• pp.13-16
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• 2016

Morphology and formation processes of lamellar grain boundaries in titanium rich binary TiAl intermetallics were studied. TiAl alloys containing aluminum content of 44 to 48 at.% were induction-heated to 1723 K followed by helium-gas-quenching at various temperatures. For the Ti-44%Al, few lamellae were observed in samples quenched from higher than 1473 K. Although small peaks of beta phase were detected using X-ray diffraction, only the ordered hexagonal phase (${\alpha}_2$) with clear APB contrast was observed in TEM observation. For the Ti-48 at.%Al alloy, almost no lamellar structure, and straight grain boundaries were observed in samples quenched from higher than 1623 K. The formation of lamellae along grain boundaries was observed in the sample quenched from 1573 K. The fully lamellar microstructures with serrated boundaries were observed in samples quenched from lower than 1473 K. It was found that the formation of ${\gamma}$ platelets took place at higher temperatures in Ti-48 at.%Al than in Ti-44 at.%Al. Although the size of the serration is different, serrated lamellar grain boundaries could be obtained for all alloy compositions employed. The serration appeared to be due to the grain boundary migration induced by precipitation and growth of ${\gamma}$. Differences in transformation characteristics with aluminum content are discussed.

• Journal of Welding and Joining
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• 제10권2호
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• pp.43-50
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• 1992

This study was aimed at resolving uncertainties about lamellar tearing initiation temperatures and studying the effect of nonmetallic inclusions on the tear initiation. In order to measure the lamellar tearing initiation temperature, the slice bend test was conducted in the temperature range of 20.deg.C to 425.deg.C on A572 Grade 50 and A588 Grade A steels. In addition, the weld restrain test was carried out to measure directly the tear initiation temperature with A572 steel. In slice bend tests, A572 steel showed the most susceptible region to lamellar tearing to be in the range of 100 to 300.deg.C, where the steel showed the minimum ductility. The observed tear initiation by the weld restraint test was to be in the range of 200to 300.deg.C. The tears became narrower and less rounded at the susceptible temperatures. It was confirmed in this study that lamellar teraring initiated during cooling from welding in the range of 200 to 300.deg.C and they were initiated by strain aging embrittlement.

• 한국재료학회지
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• 제25권8호
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• pp.398-402
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• 2015

Fundamental studies of microstructural changes and high temperature deformation of titanium aluminide (TiAl) were conducted from the view point of the effect of Al content in order to develop the manufacturing process of TiAl. Microstructures in an as cast state consisted mainly of lamellar structure irrespective of Al content. By homogenization at 1473 K, the microstructures of Ti-49Al and Ti-51Al were transformed into an equiaxial structure which was composed of ${\gamma}$-TiAl, while the lamellar structure that was observed in Ti-46Al and Ti-47Al was much more stable. We found that the reduction of Al content suppressed the formation of equiaxial grains and resulted in a microstructure of only a lamellar structure. On Ti-49Al and Ti-51Al, dynamic recrystallization occurred during high temperature deformation, and the microstructure was transformed into a fine equiaxial one, while the microstructures of Ti-46Al and Ti-47Al contained few recrystallized grains and consisted mainly of a deformed lamellar structure. We observed that on the low-Al alloys the lamellar structure under hard mode deformation conditions deformed as kink observed B2-NiAl. High temperature deformation characteristics of TiAl were strongly affected by Al content. An increase of Al content resulted in a decrease of peak stress and activation energy for plastic deformation and an increase of the recrystallization ratio in TiAl.

• Journal of Welding and Joining
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• 제6권4호
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• pp.44-53
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• 1988

The mechanical strengths of buried lamellar tears located near the weld toe in the welded tee joints were evaluated in terms of the loss of load carrying capacity as a function of tear area. In static loading, the load carrying capacity was significantly reduced when tear intercepted over 10% of the cross-sectional area of the welded joints. However, the welded joints containing buried tears still failed at stresses over the yield strength of the base metal in the through-thickness direction in spite of the presence of tears up to 20-25% of the area. Fatigue strength of welded joints containing tears markedly reduced with increasing tear areas. Lehigh lamellar tearing test used in this study to produce speicmens was described in detail. The load carrying cpapacity in static loading was influenced by the reduction of supporting area whereas that in fatigue loading was influenced by the stress-concentration effects of lamellar tears and the reduction of supporting area. In bend tests, the pre-existing lamellar tears always grew up toward the weld toe. However, in fatigue loading, cracks grew up and down simultaneously form both the weld toe and the top of lamellar tears because of stress concentration. In fatigue loading, delaminations and decohesion of inclusion/matrix interface generated in multipass welds provided crack propagation paths and enhanced crack propagation because the tips of delaminations and deconhesios acted as stress raisers.

• 설비공학논문집
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• 제28권7호
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• pp.283-287
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• 2016

One of the most important factors for determining the thermal performance of an evaporative cooling system is the wettability of the evaporative heat exchanger surface. Evaporation of a widely spread water film on the heat exchanger surface promotes heat transfer between the "dry" air and "wet" air passages. Hydrophilic coating is generally applied on the heat exchanger surfaces to increase the wettability of the heat exchanger surface and the COP of the evaporative cooling system. In this paper, a simple lamellar patterned structure is suggested to maximize the spreading of a water film on the vertically oriented walls. The capillary height of the lamellar structured grooves is analyzed through a theoretical model, and the results are compared with the numerical analysis through a finite element analysis tool, SE-FIT. A good agreement between the theoretical model and the numerical analysis can be observed as long as the channel depth is comparable to or larger than the channel width of the lamellar structure.

• 한국정밀공학회지
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• 제21권10호
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• pp.162-169
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• 2004

High temperature uniaxial compression tests in the alpha single phase region were carried out on the Ti -43mo1%Al intermetallic compound, in order to obtain oriented lamellar microstructure. The compression deformation temperatures and strain rates are from 1573k to 1623k and 1.0x10$^{-4}$ s to 5.0x10$^{-3}$ s, respectively. Fully lamellar microstructure was observed after the uniaxial compression deformation in a single phase region followed by cooling to room temperature. Lamellar colony diameter depended on strain rates and test temperatures. The diameter varied between 8601m and 300fm. Stress-strain curve showed a work softening and the size of lamellar colony diameter varied depending on peak stresses. This shows the occurrence of dynamic recrystallization. Texture measurements after the uniaxial compression deformation, showed the development of fiber during dynamic recrystallization. It is seen that the area for the maximum pole density existed in 35 degrees away from the compression plane. The texture sharpens with a decrease in strain rate

• 대한화장품학회지
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• 제35권3호
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• pp.171-177
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• 2009

본 총설에서는 세라마이드를 함유한 다양한 조성의 안정한 라멜라 구조체 제조 및 그들의 분산에 대한 기술을 소개하였다. DSC, x-ray diffraction 및 FT-IR spectra를 이용하여 라멜라 구조체의 성질을 평가했으며, 세라마이드와 함께 적절한 오일, 계면활성제, 또는 지질로 구성된 형태의 안정한 라멜라 구조체 형성을 자세히 설명하였다. 세라마이드를 이용 하기 위한 다양한 접근 방법은 에멀전 및 리포좀 제조에 이용 될 것이며 나아가 화장품, 의약품 및 약물 전달분야에 응용 할 수 있을 것이다.

• 통합자연과학논문집
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• 제1권2호
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• pp.76-78
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• 2008

A series of the long-chain iron(II) alkylsulfonate hydrates were synthesized via self-assembly of surfactant alkyl chains in aqueous medium. Reaction of iron(II) salts with n-alkylsulfonate yields lamellar $Fe(CnH2n+1SO3)2{\cdot}4H_2O$. These compounds show a layered structure, as determined by XRD, consisting of alternating organic alkylsulfonate layers and inorganic iron(II) hydrate layers, with interlayer distances of upto 3.2 nm. This lamellar structure may be attributed to the amphiphilic nature of the surfactants, mediating the coordination and H-bionding interactions, and the hydrophobic alkyl chains. An alkyl chain packing of present system are differ from those of similar Cu(II) series, which are attributed from the size of hydrated metal(II) ions.

• 한국임상수의학회지
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• 제40권4호
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• pp.303-307
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• 2023

A 4-year-old female Munchkin cat presented with a 2-day history of a large mass in the left eye. On the first presentation, slit lamp biomicroscopy revealed a large corneal bulla occupying around 40% of the corneal surface along the visual axis. Based on the results, a diagnosis of feline acute bullous keratopathy was made. Due to the location of the extensive corneal bulla, autologous lamellar keratoplasty was performed based on prior studies, to both minimize postoperative complications that may affect axial vision and address any cosmetic concerns the owner had. The autologous lamellar keratoplasty successfully resolved the corneal bulla with no signs of corneal opacities postoperatively. Therefore, autologous lamellar keratoplasty may be a useful surgical treatment for feline acute bullous keratopathy from both the tectonic and optical points of view.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.23-24
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• 2013