• Journal of Korean Society of Steel Construction
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• v.17 no.3 s.76
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• pp.357-363
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• 2005

There is a great need for high-strength steel especially for the high-rise steel building structure. High-strength steels, however, may have mechanical properties that are significantly different from those of the conventional steels. The application of high-strength steels to building structures should be reviewed as to whether the inelastic behavior equivalent to that of conventional steels can be attained or not. In this study, SM570TMC steel was tested to evaluate buckling strength under axial compressive force. The comparison tests for local buckling strength evaluation of box-type and H-shaped welded columns were performed with variable width-thickness ratios. As for the experimental check, the maximum strength of stub column was determined by local buckling as far as the limit of width-to-thickness ratio was satisfied with current design codes. Also, the strength of the stub column did not decrease suddenly by local buckling before maximum strength even when the ratio is not satisfied. The buckling strength of SM570TMC steel was higher than both ASD (Allowable Stress Design) and LRFD (Load and Resistance Factor Design) specifications.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2021-2025
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• 2007

Performance of single cell at solid oxide fuel cell (SOFC) system is largely affected by electrocatalytic and thermal properties of cathode. Samarium-based perovskite oxide material is recently recognized as promising cathode material for intermediate temperature-operating SOFC due to its high electrocatalytic property. Perovskite structured $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$ and its composite material, $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}/Sm_{0.2}Ce_{0.8}O_{1.9}$ were investigated in terms of area specific resistance (ASR), thermal expansion coefficient (TEC), thermal cycling and long term performance. $Sm_{0.2}Ce_{0.8}O_{1.9}$ was used as electrolyte material. Electrochemical ac impedance spectroscopy (EIS) and dilatometer were used to measure the cathodic properties. Composite cathode ($Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$: $Sm_{0.2}Ce_{0.8}O_{1.9}$ = 6:4) showed a good ASR of 0.13${\Omega}$ $cm^2$ at 650$^{\circ}C$ and its TEC value was 12.3${\times}$10-6/K at 600$^{\circ}C$ which is similar to the value of ceria-based electrolyte of 11.9${\times}$10-6/K. Performance of composite cathode was maintained with no degradation even after 13 times thermal cycle test.

• Rubber Technology
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• v.9 no.1
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• pp.1-12
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• 2008

Effects of silane modifier, bis(triethoxysilylpropyl) tetrasulfide (TESPT(S4)) and bis(triethoxysilylpropyl) disulfide (TESPD(S2)), on silica filled compound were investigated upon processability, dynamic, mechanical, heat build-up, blowout properties, and silica dispersion in natural rubber (NR). The temperature of the S2 treated silica compound generated higher than that of the S4 treated compound during internal mixer compounding. The shear viscosity of the S2 compound exhibited lower than that of the S4 compound and the viscosity measured in dynamic mode was close to each other. The elongation modulus of the S2 compound exhibited lower than that of the S4; however, the tear resistance strength of the S2 compound exhibited higher than that of the S4 compound. The loss tan$\delta$ values of the S2 compound exhibited higher than those of the S4 at room temperature. The augmentation of the test temperature lowered the tan$\delta$ values of each compound, which results in close tan$\delta$ values to each other at $100^{\circ}C$. The S2 compound deformed less than the S4 compound, and the blowout time of each compound was close to each other. The S2 compound generated more heat build-up than the S4 compound. The abrasion loss of the S2 compound was less than that of the S4 compound. The size of the silica agglomerate reduced on both S4 and S2 compounds upon vulcanization. The addition of the bifunctional silanes (S2 and S4) on silica filled NR compound improved the processability of each compound and their effects were more significant on the S2 compound than the S4 compound. After vulcanization the silica agglomerate size of each compound reduced compared with before vulcanization.

• Journal of Chest Surgery
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• v.36 no.7
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• pp.527-530
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• 2003

Reexpansion pulmonary edema is a rare complication of the treatment of lung collapse secondary to pneumothorax, pleural effusion, or atelectasis. But occasionally, severe morbidity and death may result. Reexpansion pulmonary edema occurs when chronically collapsed lung is rapidly reexpanded by evacuation of large amounts of air or fluid. In the treatment of the chronically collapsed lung, physicians must remember the possible events and prevent the complications. When the difference in airway resistance or lung compliance between the two lungs is exaggerated, conventional mechanical ventilation might lead to preferential ventilation with hyperexpansion of one lung and gradual collapse of the other. Differential ventilation has been advocated to avert this problem. By differential lung ventilation, we successfully treated a severe reexpansion pulmonary edema in two patients. Therefore we suggest that differential lung ventilation is the treatment of choice for severe reexpansion pulmonary edema.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.265-273
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• 2009

There have been numerous studies to develop eco-friendly concrete. The attempt to reduce the amount of cement used is suggested as one of the solutions for eco-friendly concrete. To decrease the usage of cement, the pozzolan reaction materials are used as a mineral admixture. Hwang-toh, which is broadly deposited in Korea is a well known environment friendly material and the activated hwang-toh, which has the property of pozzolan reaction, is alternatively used as a mineral admixture of concrete. The purpose of this study is to investigate the drying shrinkage of hwang-toh concrete mixed with recycled PET fiber. Therefore, drying shrinkage experiments are performed to analyze mechanical property of hwang-toh concrete mixed with recycled PET fiber. Test results showed that the drying shrinkage is controlled by hwang-toh admixture and PET fiber.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.09a
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• pp.233-241
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces strictly related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.09a
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• pp.211-219
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces stric시y related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials. In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.71-80
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• 2013

Fire-resistant (FR) test data for a square concrete-filled steel tube (CFT) columns consisting of high-strength steel (fy>650MPa) and high strength concrete (fck>100MPa) under axial loads are insufficient. The FR behavior of square high-strength CFT members was investigated experimentally for two specimens having ${\Box}-400{\times}400{\times}15{\times}3,000mm$ with two axial load cases (5,000kN and 2,500kN). The results show that the FR performance of the high-strength CFT was rapidly decreased at earlier time (much earlier at high axial load) than expected due to high strength concrete spalling and cracks. In addition, a fiber element analysis (FEA) model was proposed and used to simulate the fiber behaviour of the columns. For steel and concrete, the mechanical and thermal properties recommended in EN 1994-1-2 are adopted. Test results were compared to those of numerical analyses considering a combination of temperature and axial compression. The numerical model can reasonably predict the time-axial deformation relationship.

• Journal of Welding and Joining
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• v.34 no.3
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• pp.61-68
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• 2016

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E91T1-B9C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, tempered martensite and lower bainite were formed in first layer of weld metal. The amount of tempered martensite was decreased and the amount of lower bainite was increased with increasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered Martensite and lower Bainite. Tensile strengths of dissimilar welds decreased with increasing heat inputs. Dissimilar welds seemed to have a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals showed that the corrosion rate increased with increasing heat inputs due to the increase of the amount of lower Bainite.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5A
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• pp.379-387
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• 2011

According to the development of ultra-high performance concrete (UHPC), its mechanical performance have been known as superior than normal and/or high performance concrete. However, its construction and structural safety must have studied with revisions and supplements. In this study, tests have been performed on UHPC precast segment joint with different levels of joint types and lateral forces under direct shear. From the results of the experimental tests, it can be concluded that the properties of the referred joints are significant for the resistance of shear behavior, and the increase of lateral force in these joints may suggest as critical lateral stress on that behavior.