• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.71-72
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.751-752
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• 2013

• Journal of the Korean Data and Information Science Society
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• v.23 no.6
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• pp.1259-1269
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• 2012

Cloud computing has rapidly become a new infrastructure for organizations to reduce their capital cost in IT investment and to develop planetary-scale distributed applications. One of the fundamental challenges in geographically distributed clouds is to provide efficient algorithms for supporting inter-cloud data management and dissemination. In this paper, we propose a geographic group quorum system (GGQS)-based hybrid algorithm for improving the interoperability of inter-cloud in time-critical event dissemination service, such as computing policy updating, message sharing, event notification and so forth. The proposed algorithm first organizes these distributed clouds into a geographic group quorum overlay to support a constant event dissemination latency. Then it uses a hybrid protocol that combines geographic group-based broad-cast with quorum-based multicast. Our numerical results show that the GGQS-based hybrid algorithm improves the efficiency as compared with Chord-based, Plume an GQS-based algorithms.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.175-185
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• 2013

Currently in precast concrete construction, precast concrete and cast-in-place concrete with different concrete strengths are used. However, current design codes do not provide shear design methods for PC-CIP hybrid members using dual concrete strengths. In the present study, the shear strengths of beams using dual concrete compressive strengths (24 MPa, 60 MPa) were tested. The test variables were the area ratio of the two concretes, longitudinal bar ratio, and shear span-to-depth ratio. The shear strengths of test specimens were evaluated by current design methods, using an effective concrete strength (considering the area ratio of the two concrete strengths). The test result showed that when 60 MPa concrete was used in the compressive zone and the longitudinal bar ratio was low, the shear strengths of the test specimens were less than the predictions. On the basis of the results, design recommendations were provided for the shear design of the PC-CIP hybrid beams.

• Journal of Korea Foundry Society
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• v.14 no.3
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• pp.258-266
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• 1994

AC4A $Al/Al_2O_3+SiC_p$ hybrid composites were fabricated by the squeeze infiltration technique. Effect of applied pressure, volume fraction of reinforcement($Al_2O_3$ and SiC) and SiC particle size($4.5{\mu}m$, $6.5{\mu}m$ and $9.3{\mu}m$) on the solidification microstructure of the hybrid composites were examined. Mechanical properties were estimated preliminarly by fractographic observation, hardness measurement and wear test. Results show that the microstructure of the hybrid composites were quite satisfactory, namely revealing relatively uniform distribution of reinforcements and refined matrix. Some aggregation of SiC particle caused by particle pushing was observed especially in the hybrid composites containg in fine particle($4.5{\mu}m$). Refined matrix was attributed to applied pressure and increased nucleation sites with addition of reinforcements. Fractured facet also revealed finer for the hybrid composites possibly due to refined matrix. Hardness and wear resistance increased with volume fraction of reinforcements. For hybrid composites with $9.3{\mu}m$ SiC, hardness was somewhat lower and wear resistance higher than other composites.

• Computers and Concrete
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• v.26 no.3
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• pp.257-273
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• 2020

Concrete bond strength with steel re-bars depends on multiple factors including concrete-steel interface and mechanical properties of concrete. However, the hydration development of cementitious paste, and in turn the mechanical properties of concrete, are negatively affected by cold weather. This study aimed at exploring the concrete-steel bonding behavior in concrete cast and cured under freezing temperatures. Three concrete mixtures were cast and cured at -10 and -20℃. The mixtures were protected using conventional insulation blankets and a hybrid system consisting of insulation blankets and phase change materials. The mixtures comprised General Use cement, fly ash (20%), nano-silica (6%) and calcium nitrate-nitrite as a cold weather admixture system. The mixtures were tested in terms of internal temperature, compressive, tensile strengths, and modulus of elasticity. In addition, the bond strength between concrete and steel re-bars were evaluated by a pull-out test, while the quality of the interface between concrete and steel was assessed by thermal and microscopy studies. In addition, the internal heat evolution and force-slip relationship were modeled based on energy conservation and stress-strain relationships, respectively using three-dimensional (3D) finite-element software. The results showed the reliability of the proposed models to accurately predict concrete heat evolution as well as bond strength relative to experimental data. The hybrid protection system and nano-modified concrete mixtures produced good quality concrete-steel interface with adequate bond strength, without need for heating operations before casting and during curing under freezing temperatures down to -20℃.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.67-70
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• 2000

Mechanical properties of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites fabricated by the reaction squeeze casting were compared with those of (15%$AI_20_3{\cdot}SiO_2$)/Al composites. Intermetallic compound formed by reaction between molten aluminum and reinforcing powder was uniformly distributed in the Al matrix. These intermetallic compounds were identified as $Al_3$NI using EDS and X-ray diffraction analysis. Microhardness and flexural strength of hybrid composites were higher than that of (15%$AI_20_3{\cdot}SiO_2$)/Al Composite. In-Situ fracture tests were Conducted on (15%$AI_20_3{\cdot}SiO_2$)/Al Composites and (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites to identify the microfracture process. It was identified from the in-situ fracture test of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al composites, microcracks were initiated mainly at the short fiber / matrix interfaces. As the loading was continued, the crack propagated mainly along the separated interfacial regions and the well developed shear bands. It was identified from the in-situ fracture test of (10%$AI_20_3{\cdot}SiO_2$+5%Ni)/Al hybrid composites, microcracks were initiated mainly by the short fiber/matrix interfacial debonding. The crack proceeded mainly through the intermetallic compound clusters

• Journal of the Korean Geosynthetics Society
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• v.4 no.4
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• pp.47-56
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• 2005

With the need of efficient site use retaining walls have frequently used. Of them dry cast modular block wall(MBW), in which geogrid and concrete block are used is getting popular because of its simplicity and economical efficiency of construction. However, since this method is based on the theory of earth pressure, sands with good quality should be used. In contrast, reinforced soil slope(RSS) that the slope is less than $70^{\circ}$ can use wider range of soil than MBW. A hybrid reinforced geo-structure might be a good alternative in view of overcoming difficulty obtaining soils with good quality as well as maximizing the efficiency of site use. This method is composed of reinforced block wall and reinforced soil slope. In this method, reinforced block wall is constructed up to a certain height vertically at ground boundary first. Reinforced soil slope is then constructed on the block wall subsequently. This paper introduces several technical points that should be taken into account in design and construction.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.143-146
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• 2002

Mg alloy is the lightest material of structural materials and is noticed for lightweight automotive parts because of excellent castability, superior ductility and damping capacity than Al alloy. But Mg Alloy is poor corrosion resistance and high temperature creep properties. In this study, Mg Matrix Composites were fabricated by squeeze casting method to improve high temperature creep properties and damping capacity. Hybrid Mg composites reinforced with Alborex, graphite particle, and SiCp was improved creep properties and damping capacity compared with Mg alloy. Compared to the length ($9\mu\textrm{m}, 27\mu\textrm{m}, 45\mu\textrm{m} etc.$), Hybrid Mg composites reinforced with SiCp, one of the most superior of the length and Alborex were more superior than those reinforced with graphite particle and Alborex in mechanical properties, creep characteristics, and damping capacity, etc.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.294-301
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• 2011

A two-dimensional hybrid flaw solver has been developed for the accurate and efficient simulation of steady and unsteady flaw fields. The flow solver was cast to accommodate two different topologies of computational meshes. Triangular meshes are adopted in the near-body region such that complex geometric configurations can be easily modeled, while adaptive Cartesian meshes are, utilized in the off-body region to resolve the flaw more accurately with less numerical dissipation by adopting a spatially high-order accurate scheme and solution-adaptive mesh refinement technique. A chimera mesh technique has been employed to link the two flow regimes adopting each mesh topology. Validations were made for the unsteady inviscid vol1ex convection am the unsteady turbulent flaws over an NACA0012 airfoil, and the results were compared with experimental and other computational results.