• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.844-851
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• 2009

A soil mixture with low permeability and bentonite as an additive has been highly utilized as a cutoff material in landfills, banks, and dams. Even though it is anticipated that the water can seep through shear failures in the filter layer due to external loads and embankment loads during construction, usually only the coefficient of permeability of the soil mixture is considered rather than the changes of strength from the different amounts of additives. Therefore, the amount of bentonite was changed between 0%~4% in the soil mixture of the bed material to conduct a series of unconfined compressive strength, tensile strength, and shear strength tests on a specimen in order to study the characteristics of the strength. In the result, the unconfined compressive and tensile strength were increased along with the increased amount of bentonite in the low water content; however, the tensile strength in the consolidated-drained shear test generally showed similar values without significant changes.

• Transactions on Electrical and Electronic Materials
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• v.13 no.6
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• pp.301-304
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• 2012

Epoxy/microsilica (65 phr)/nanosilica (0~5 phr) composites (EMNC) were prepared in order to develop a high-voltage insulation material, where phr means parts per hundred relative to the epoxy oligomer. Tensile and flexural tests of the composites were carried out, and the AC electrical breakdown strength was measured, after which all the data were estimated by Weibull statistical analysis. As the nanosilica content increased, the tensile strength increased, and the highest value was 117.7 MPa in the EMNC system with 3 phr nanosilica, which was ca. 10% higher than that of the system without nanosilica. The value then decreased after 3 phr. The flexural strength and AC electrical breakdown strength showed the same tendencies as the tensile strength. The highest value of the flexural strength was 184.6 MPa in the EMNC system with 3 phr of nanosilica, which was ca. 15% higher than that of the system without nanosilica. The strongest value of the AC electrical breakdown strength was 79.0 kV/0.5 mm in the EMNC system with 3 phr of nanosilica, which was ca. 34% higher than that of the system without nanosilica.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.48-69
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• 1997

The use of advanced composite materials in many engineering structures has steadily increased during the last decade. Advanced composite materials allow the design engineer to tailor the directional stiffness and the strength of materials as required for the structures. Design variables to the design engineer include multiple material systems. ply orientation, ply thickness, stacking sequence and boundary conditions, in addition to overall structural design parameters. Since the vibration and impact strength of composite cylindrical shell is an important consideration for composite structures design, the reliable prediction method and design methodology should be required. In this study, the optimum design of composite cylindrical shell for maximum natural frequency, buckling strength and impact strength are developed by analytic and numerical method. The effect of parameters such as the various composite material orthotropic properties (CFRP, GFRP, KFRP, Al-CFRP hybrid), the stacking sequences, the shell thickness, and the boundary conditions on structural characteristics are studied extensively.

• Structural Engineering and Mechanics
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• v.12 no.1
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• pp.71-84
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• 2001

The objective of this paper is to develop a simplified method that could predict the strength of concrete filled steel tube (CFT) columns applicable to high strength material under combined axial compression and flexure. The simplified method for determining the strength of CFT columns is based on the interaction curve of the section approached by a polygonal connection of the points. These points are determined by using symmetrical properties of the CFT section. For each point, a simple equation is proposed to determine the strength of the slender columns under compression and flexure. The simple equation was adjusted with results of elasto-plastic analysis results. Validation of the simplified method is undertaken by comparison with data from the test conducted at Kyushu University. These results confirm the fact that the simplified method could accurately and reliably predict the strength of CFT columns under combined axial compression and flexure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.586-588
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• 2001

Inner part of FRP specimen was made unidirectionally by pultrusion method and outer part of FRP was made by filament winding method to study the effect of fiber orientatons on the strength of FRP. The strength of bending and compression was simulated and evaluated. The results of simulated strength and evaluated strength were different greately each other. The stress which affect the feature of FRP was simulated to investigate the difference of the results between simulation and evaluation Shear stresses were investigated to the main stress to affect the fracture of FRP.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.45-48
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• 2006

Generally, the strength of concrete depends on factors of materials, mix proportions, compaction, manufacturing methods and curing and so on. This is an experimental study to compare and analyze the influence of cementitious material type on the compressive strength of ultra high strength concrete. For this purpose, the mix proportions of concrete according to the type of cementitious materials(Fly ash, blast furnace slag, silica fume) and W/B(31.5, 27.5%) was selected. And then air content, slump-flow, O-lot, compressive strength test were performed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.119-126
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• 2006

The elastic budding strength of a GFRP pipe reinforced with ribs was evaluated. The height and thickness of a rib and the spacing between two adjacent ribs were considered as factors affecting tlje budding strength of the pipe. And also, the ratio of the longitudinal stiffness and transverse stiffness was considered as the parameter affecting on the budding strength because GFRP is orthotropic material. Buckling strengths of various GFRP pipe models with different shapes and stiffness ratio were evaluated by FE analyses and a formula to estimate the elastic buckling strength of a rib-reinforced pipe made of orthotropic material was suggested from the regression with FE analysis results. Analysis results show that a rib-reinforced pipe has superior buckling strength to a general flat pipe and the suggested formula estimates accurate buckling strength of the rib-reinforced pipe.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.597-602
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• 1997

The compressive strength of horizontal joints in precast concrete large panel structures depends on parameters such as grout and panel strength, detail of joint, joint moment, width of grout column etc. As the panels are only connected at the pocket, it results in the reduction of compressive strength area. The purposes of this study are to develop the suitable grout material the joint pocket and to enable us to evaluate structural capacity. The validity of the design formulas provides us more economic system in construction. Test results of 15 specimens show that the proper construction procedure and grouting material develop the sufficient compressive strength of the wall as monolithic system.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.53-56
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• 2008

Modern society is experiencing a high population density and a centralization of facilities. The clear trends in the construction field are aggrandizement, elevation and specialization of building structures. Such trends require improvements of skills in raising material performances, structuring, planning, designing, and increasing construction capacities. In order to procure high performance materials and construction techniques, a top-quality concrete should be used since it takes up a large part of the material. In recent years, active researches have been done on the ultra high strength concrete. Therefore, this experimental study is strength management to fixed quantity in the field of ultra-strong concrete.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.239-242
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• 1999

In this study, we evaluates the dependence of thickness and temperature in the breakdown strength of MDPE and effect of semiconductor. As the result, breakdown strength trend to decrease according to the increase of thickness and temperature but there is no dependence of temperature in the 70${\mu}{\textrm}{m}$ MDPE film. We obtained the result that the breakdown strength was a little lower in the structure of Semil/MDPE than Semi/MDPE/Semi, but breakdown strength of MDPE was greater both of all. Therefore we are investigating the effect of semiconductor in the breakdown strength.