• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.39-47
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• 2004

In this paper, the defects of two-dimensional anisotropic elastic bodies are identified by using the boundary element method. The use of numerical models that contain only boundary integral terns reduces the dimensionality of the problem by one. This advantage is particularly important in problems such as crack mechanics. Avoiding domain meshing is also particularly advantageous in the solution of inverse problems since it overcomes mesh perturbations and simplifies the procedure. In this paper, nondestructive approaches for the existing isotropic materials are extended to analyze the elastic bodies made of anisotropic materials such as composites. After verifying that the proposing boundary element model is in good agreement with numerical results reported by other investigators, the effect of noise in the measurements on the identifiability is studied with respect to different design parameters of layered composites. Sample studies are carried out for various layup configurations and loading conditions. The effects of the layup sequences in detecting flaw of composites is explored in this paper.

• Journal of the Korean Geosynthetics Society
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• v.9 no.4
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• pp.17-25
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• 2010

Evaluation of stability in traditional designing of reinforced soil structures is executed by examination of internal and external stability. Analysis of internal stability is for pull-out and ductile strength. Analysis of external stability is for settlement, overturning and sliding. To minimize inherent uncertainties of soil properties and analytical model, reliability analysis was developed recently. In this study, reliability analysis method considering simultaneous failure probability for various failure mode of internal and external stability is proposed. By applying uni-modal bounds, Stability of system reliability of reinforced soil structures is evaluated by integrating multi failure mode for various analytical model. Because of complex consideration for various failure shapes and modes, it is possible to secure advanced safety by using simultaneous failure probability. And evaluation of reinforced soil structure is executed by representative index, simultaneous failure probability, than previous method.

• Journal of the Korean Geosynthetics Society
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• v.14 no.4
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• pp.11-21
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• 2015

The method to replace asphalt and cement is needed to reduce the carbon emission on road. Polymeric material which is light and easy to handle while having complex function with less carbon emission would be highly effective when it replaced soil pavement containing cement. This study is intended to identify the usability of soil pavement containing organic solidification agent only through the field test. Pavement on bike trail still satisfied required bearing capacity coefficient in 3 months. Pavement after passing 1.6 bil units of bike through pavement acceleration test that simulated a long-term serviceability during a short-time still remained unaffected, demonstrating a long-term serviceability of soil pavement.

• Korean Journal of Food Science and Technology
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• v.36 no.6
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• pp.991-994
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• 2004

Effects of formulation KTG075 from edible plants on intestinal function, particularly on Mucin 2 secretion, were examined by loperamide-induced constipation method using Sprague Dawley rats (SD rats, male). Crypt epithelial cells containing more mucus and mucus layer stained with alcian blue were significantly thicker in KTG075 group than control group. When Biogenex AM358 of antibody against Mucin 2 was used, crypt epithelial cells secreted more Mucin 2 in KTG075 group than control group. The Mucus layer at fecal surface was thinner and less mucus was recovered from mucosal surface in constipated rats than in KTG075 group. Mucus production of crypt epithelial cells and mucus contents at fecal and mucosal surfaces were reduced by loperamide-induced constipation. These results indicate formula KTG075 accelerates evacuation and activates intestines.

• Journal of the Korean Geosynthetics Society
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• v.4 no.1
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• pp.7-15
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• 2005

In recent years, the geotextile tubes filled with dredged material have been used in dike and breakwater construction for a number of projects around the world, and their use in this field is growing very fast. One of the most attractive advantages of geotextile tube technology is can be use the in-situ filling materials by hydraulic pumping, it can be also established lower costs and fast construction than other technology. Geotextiles form one of the two largest groups of geosynthetics and it is commonly made by two major types of polymer material(Polypropylene, Polyester). The objective of this paper is to examine several issues associated with drainage function and feasibility of geotextile tube structure such as filtering efficiency, dewatering efficiency, and filling process with polymer materials. Based on the laboratory filtering test and in-situ tests, polypropylene goetextile is more effective for drainage function of geotextile tube technology.

• Journal of the Korean Geosynthetics Society
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• v.2 no.1
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• pp.47-55
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• 2003

The effects of fiber composition factors of 14 geotextiles which are thickness, porosity, fiber length and diameter etc. on the transmissivity were examined and in-plane permeability of geotextiles under thickness change, transmissivity, confined load were analyzed by the constitutive equations. And the effects of laminar structure on the permittivity of laminar geotextile composites which were manufactured with fiber packing densities were assessed. Transmissivities were increased with thickness of geotextiles and in-plane permeability coefficients were increased with porosity and fiber diameter. The effects of porosity were decreased with normal stress and slightly increased with fiber length. Transmissivities were increased with fiber diameter and showed same tendensy for the same fiber length. Permittivities of laminar geotextile composites were influenced by the waterhead loss in the inner interface and the connection shape of these composites to water path was interpreted as bell mouth type or soft flux pipe type.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.189-197
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• 2018

A sprayable waterproofing membrane which has relatively high adhesive property onto concrete enables faster construction with better waterproof performance compared with a conventional sheet membrane. However, the sprayable waterproofing membrane is a recently developed material and its performance and behavior with structures are not sufficiently reported. Therefore, in this study, the shear behavior of sprayable waterproofing membrane was numerically analyzed using the results of previous studies of composite shotcrete with sprayable waterproofing membrane. From the previous study, shear behavior of shotcrete with sprayable waterproofing membrane was different from shotcrete case and there was a limitation to express the behavior of the interface in general shear strength method. Therefore, in this study, the direct shear test was numerically simulated using two contact models, and then the best suitable method to express the shear behavior of the sprayable waterproofing membrane was suggested.

• Korean Journal of Metals and Materials
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• v.49 no.7
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• pp.565-569
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• 2011

Nanopowders of MgO, $Al_2O_3$ and $SiO_2$ were made by high-energy ball milling. The fast sintering of nanostructured $Al_2O_3-MgSiO_3-SiO_2$ composites was investigated from mechanically activated powders of MgO, $Al_2O_3$ and $SiO_2$ by a pulsed-current activated sintering process. Nanocrystalline materials have received much attention as advanced engineering materials with improved physical and mechanical properties; in particular greater strength, hardness, excellent ductility and toughness. Highly dense nanostructured $Al_2O_3- MgSiO_3-SiO_2$ composites were produced with simultaneous application of 80 MPa and pulsed output current of 2800A within 2 minutes. The sintering behavior, grain size and mechanical properties of $Al_2O_3-MgSiO_3-SiO_2$ composites were investigated.

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.310-315
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• 2012

Nano-powders of 1.5TiAl and $Al_2O_3$ were synthesized from $1.5TiO_2$ and 3Al powders by high energy ball milling. Nanocrystalline $Al_2O_3$ reinforced composite was consolidated by pulsed current activated sintering within 2 minutes from mechanochemically synthesized powders of $Al_2O_3$ and 1.5TiAl. The relative density of the composite was 99.5%. The average hardness and fracture toughness values obtained were $1250kg/mm^2$ and $10MPa{\cdot}m^{1/2}$, respectively.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.449-455
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• 2021

Composite materials are substances that are configured to have excellent physical properties by combining the properties of a single substance, and are in the limelight as materials that exceed the performance of metals and polymers. However, it has the disadvantages of long cycle time and high unit price, and much research is being performed to overcome these disadvantages. In this study, we developed an epoxy resin curing agent that can shorten the time required for mass production of composite materials, and tried to expand the applicability of objections by imparting flame retardancy. The epoxy resin used as a basic substance utilized two types of bisphenol F and resorcinol structure, which was further modified using 9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide (DOPO) to impart flame retardancy. Triethylphosphate (TEP) and bis [(5-ethyl-2-methyl-1,3,2-dioxaphosphorinan-5-yl)methyl] methyl phosphonate P,P'-dioxide (FR-001) were used as additives, seven kinds of compositions were blended, thermal characteristics (gelation time, glass transition temperature) and flame retardant performance were evaluated. We successfully developed an epoxy matrix that can be applied to high pressure resin transfer molding (HP-RTM) process.