• International Journal of High-Rise Buildings
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• v.5 no.3
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• pp.177-186
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• 2016

Along the subduction-zone of the western Japanese islands, large earthquakes are expected occur around the middle of this century, and long-period ground motions will reach major urban areas, shaking high-rise buildings violently. Since some old high-rise buildings were designed without considering long-period ground motions, reinforcing such buildings is an important issue. An effective method to reinforce existing high-rise buildings is installing additional dampers. However, a problem with ordinary dampers is that they require reinforcement of surrounding columns and girders to support large reaction forces generated during earthquake ground motion. To solve this problem, a deformation-dependent oil damper was developed. The most attractive feature of this damper is to reduce the damping force at the moment when the frame deformation comes close to its maximum value. Due to this feature, the reinforcement of columns, girders, and foundations are no longer required. The authors applied seismic retrofitting with a deformation-dependent oil damper to an existing 54-story office building (Shinjuku Center Building) located in Shinjuku ward, Tokyo, in 2009 to suppress vibration under the long period earthquake ground motions. The seismic responses were observed in the 2011 Tohoku Earthquake, and it is clarified that the damping ratio was higher and the response lower by 20% as compared to the building without dampers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.7
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• pp.275-282
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• 2016

MILD (Moderate and Intense Low-oxygen Dilution) combustion using oxygen as an oxidizer is considered as one of the most promising combustion technologies for high energy efficiency and for reducing nitrogen oxide and carbon dioxide emissions. In order to investigate the effects of nozzle angle and oxygen velocity conditions on the formation of oxygen-MILD combustion, numerical and experimental approaches were performed in this study. The numerical results showed that the recirculation ratio ($K_V$), which is an important parameter for performing MILD combustion, was increased in the main reaction zone when the nozzle angle was changed from 0 degrees to 15 degrees. Also, it was observed that a low and uniform temperature distribution was achieved at an oxygen velocity of 400 m/s. The perfectly invisible oxy-MILD flame was observed experimentally under the condition of a nozzle angle of $10^{\circ}$ and an oxygen velocity of 400 m/s. Moreover, the NOx emission limit was satisfied with NOx regulation of less than 80 ppm.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.265-274
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• 2007

A study has been conducted to clarify NO emission behavior through preferential diffusion effects of $H_2$ and H in methane-hydrogen diffusion flames. A comparison is made by employing three species diffusion models. Special concerns are focused on what is the deterministic role of the preferential diffusion effects in flame structure and NO emission. The behavior of maximum flame temperatures with three species diffusion models is not explained by scalar dissipation rate but the nature of chemical kinetics. The preferential diffusion of H into reaction zone suppresses the populations of the chain carrier radicals and then flame temperature while that of $H_2$ produces the increase of flame temperature. These preferential diffusion effects of $H_2$ and H are also discussed about NO emissions through the three species diffusion models.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1101-1109
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• 2004

Experimental measurements of flame structure and soot characteristics were performed fur ethene inverse diffusion flames (IDF). IDF has been considered as the excellent flow field to study the incipient soot because soot particle do not experience the oxidation process. In this study, LIF image clarified the reaction zone of IDF with OH signal and PAH distribution. laser light scattering technique also identified the being of soot particle. To address the degree of soot maturing, C/H ratio and morphology of soot sample were investigated. From these measurements, the effect of flow residence time and temperature on soot inception could be suggested, and more details on soot characteristic in the IDF was determined according to fuel dilution and flame condition. The fuel dilution results in a decrease of temperature and enhancement of residence time, but the critical dilution mole fraction is existed for temperature not to effect on soot growth. Also, the soot inception evolved on the specific temperature and its morphology are independent of the fuel dilution ratio of fuel.

• Journal of Korea Foundry Society
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• v.15 no.6
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• pp.566-573
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• 1995

In this study, the microstructural characteristics such as primary silicon, eutectic silicon, $SiC_p$ dispersion behavior, compound amount and Si solubility in $Al/SiC_p$ composite fabricated by the squeeze casting under various conditions were investigated systematically. As applied pressure(MPa) increases, cooling rate and compound amount are increased. In gravity casting, the cooling rate of hypereutectic composite is slower than of hypoeutectic composite by exothermic reaction of primary Si crystallization. But the cooling rate of hypereutectic composite is faster than that of hypoeutectic composite fabricated by same applied pressure, because amount of primary Si crystallization in hypereutectic composite was decreased, on the contrary, primary ${\alpha}-Al$ in hypoeutetic composite was increased due to increase of Si solubility in matrix by applied pressure. The crystalized primary silicon in hypereutectic composite fabricated by squeeze casting become more fine than that in non-pressure casting This is because mush zone became narrow due to increase of Si content of eutectic composition by pressure and time for growth of primary silicon got shorter according to applied pressure. It is turned out that eutectic temperature and liquidus are decreased by the increasing of squeeze pressure in all the composite due to thermal unstability of matrix owing to increasing of Si solubility in matrix by the increasing of applied pressure, as indicated in thermal anaiysis(DSC) results.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.65-70
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• 2001

OH radical and NOx have been measured in a methane-air partially premixed flame using PLIF technique to define preheated air combustion characteristics. The temperature of mixture is determined by 300K, 400K, 600K and 800K below the auto-ignition temperature respectively. Flame height increases as equivalence ratio increased. As initial enthalpy is supplied, the radius of flame was increased and much amount of yellow flame in rich equivalence ratio was observed. This is due to the faster burning velocity. Also initial oxidization begins earlier as the initial temperature of mixture increased. It means that height of premixed flame front decreased. This phenomenon can be observed OH PLIF image. The qualitative analysis of OH concentration in the PLIF image shows that overall OH concentration increases with equivalence ratio and the initial temperature of mixture increased. At the preheating temperature goes up, axial gradient of OH concentration is less steep than that of lower temperature condition. This may identify that combustion reacts continuously, so preheated air combustion can evade the local heating and make high temperature indiscriminately in the overall reaction zone.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.73-78
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• 2005

The surface-reacted layer of titanium castings greatly affects their mechanical properties. This study analyzed the interfacial zone of Ti-20%Zr-5%Cr alloy castings obtained from phosphate bonded investment and examined the relationship between the surface-reacted layer and hardness. The Vickers hardness of cast disks were tested at 20$\mu m$ intervals from the surface to 120$\mu m$ in depth. The cross-section was observed metallurgically, and line profile of the reacted layer was conducted under the EDX. The surface-reacted layer of Ti-20%Zr-5%Cr alloy is showed a similar tendency to Ti-6%Al-4%V alloy in thickness, and also Si diffusion in multiple reacted layer of Ti-20%Zr-5%Cr alloy is less than cp Ti and similar to Ti-6%Al-4%V alloy. The Vickers hardness in the surface layer was greater than in the inner part, and the Vickers hardness of Ti-20%Zr-5%Cr alloy ranged 650 to 390 and cp Ti ranged 810 to 160, Ti-6%Al-4%V alloy ranged 710 to 530 respectively.

• Computers and Concrete
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• v.21 no.4
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• pp.471-484
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• 2018

Refined analysis depicting mass transportation and physicochemical reaction and reasonable computing load with acceptable DOFs are the two major challenges of numerical simulation for concrete durability. Mesoscopic numerical simulation for chloride diffusion considering binder, aggregate and interfacial transition zone is unable to be expended to the full structure due to huge number of DOFs. In this paper, a multiscale approach of combining both mesoscopic model including full-graded aggregate and equivalent macroscopic model was introduced. An equivalent conversion of chloride content at the Interfacial Transition Layer (ITL) connecting both models was considered. Feasibility and relative error were discussed by analytical deduction and numerical simulation. Case study clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Difference for single-scale simulation and multiscale approach was observed. Finally, this paper addressed some worth-noting conclusions about the chloride distribution and rebar corrosion regarding the configuration of rebar placement, rebar diameter, concrete cover and exposure period.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.489-495
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• 2000

The 185 ribosomal RNA gene (185 rDNA) of the marine alga Porphyra sp. 723 (Bangiales, Rhodophyta) was amplified using the polymerase chain reaction and its sequence was analysed. The Porphyra species was a summer strain collected on rocks in upper intertidal zone at Ikidae, Pusan on 23rd July 1999. The fronds were $1{\~}5 cm$ long, monostromatic, and orbicular or ovate shaped, They had spinulate processes at margin of the frond, Comparison of this 185 rDNA sequence with the other Forphyra species indicates that Porphyra sp. 723 has the same 185 rDNA sequence derived from Porphyra suborbiculata (NCBI access number; AB 013180) except one base pair substitution in 2327 base pairs.

• Korean Journal of Microbiology
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• v.38 no.4
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• pp.235-240
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• 2002

Protease producing bacterium, PB16 was isolated from food processing wastewater sludge and paddy field soil samples and selected by the clear zone and enzyme activity test. The isolate was gram negative, rod type and its protease productivity was 6.49 U/ml. As a result of API20NE kit test and 16S rDNA sequencying, the isolated PB16 was identified as Aeromonas hydrophila (99%). The growth rate ($h^{-1}$) was 0.21 in synthetic waste water only and 0.26 in synthetic waste water containing vitamin and mineral using a bioscreen C. Synthetic wastewater removal rate was 59 and 87%, respectively after 1 and 3 day reaction (intial CODcr was 2,472 mg/l).