• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.243-251
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• 2022

The purpose of this study is to investigate experimentally the effect of polyethylene fibers with different tensile strength and aspect ratio on the properties of cementless composite. Three types of mixtures according to the types of polyethylene fibers and water-to-binder ratio were prepared and density, compressive strength and tension tests were performed. Test results showed that the mixture reinforced by polyethylene fiber with a low tensile strength by 10 % and a high aspect ratio by 8.3 % had a high tensile strain capacity by 11.7 %, a high toughness by 12.4 %, and a low crack width by 9.1 %. It was also observed that high tensile strain capacity and better cracking pattern could be achieved by increasing the water-to-binder ratio of composite although its strength is low.

• Carbon letters
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• v.14 no.2
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• pp.105-109
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• 2013

Effects of the amount of nickel powder (Ni) in Ni-carbon fiber (CF) hybrid filler systems on the conductivity(or resistivity) and thermal coefficient of resistance (TCR) of filled high density polyethylene were studied. Increases of the resistivity and TCR with increasing Ni concentration at a given hybrid filler content were observed. Using the fiber contact model, we showed that the main role of Ni in the hybrid filler system is to decrease the interfiber contact resistance when Ni concentration is less than the threshold point. The formation of structural defects leading to reduced reinforcing effect resulted in both a reduction of strength and an increase of the coefficient of thermal expansion in the composite film; these changes are responsible for the increases of both resistivity and TCR with increasing Ni concentration in the hybrid filler system.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.510-515
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• 2004

A proton exchange membrane fuel cells(PEMFC) operate at low temperature, allowing for faster startups and immediate response to change in the demand for power, and also deliver high power density. To maximize economical efficiency in PEMPC, it is necessary to the optimization. Response surface method(RSM) has non-gradient and fast convergency characteristics. Sampling points are extracted by design of experiments using Central Composite Method. In this paper, it is shown that the optimization is required for the design study of the PEMFC.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1796-1803
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• 2015

While considering the current scenario, in this world power demand goes on increases day by day. Frequent power outages occur in high voltage transmission line due to the deprived performance of polluted insulators; this affects overall operation of power system and may indirectly impinge on the growth of production sector. Many researchers are keenly taking efforts to provide highly reliable and stable power to neediest. In this paper, A.C pollution flashover performance of disc type glass insulator and composite long rod insulators investigation under various artificial pollutions by varying Equivalent Salt Density Deposition (ESDD) levels. Here, we use different types of pollution methods like binding method, dipping method and spraying methods with different types of pollutants concentration. Based on dimensional analysis, four different Mathematical models have been developed to predict the A.C pollution Flashover Voltage (FOV) of insulators. Both the experimental and mathematically modeled results are compared; it's observed that mathematical model 3 yields better results.

• The Korean Journal of Ceramics
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• v.7 no.2
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• pp.74-79
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• 2001

Alumina composite reinforced by chopped alumina fiber was fabricated by filter-pressing the fiber slurry followed by the infiltration of alumina slurry. The chopped fiber was coated with nickel by electroless plating method. The green samples were densified by hot-pressing. Microstructures were studied by SEM and the mechanical properties such as bending strength and fracture toughness were measured. The resulting mechanical properties were analyzed in relation with processing parameters such as preform density and resulting microstructures. The load-displacement curve of the specimen with Ni interlayer but without Ni inclusion showed brittle fracture mode due to the direct contact between matrix and fiber. The load-displacement curve of the specimen with Ni interlayer and Ni inclusion in the matrix which is introduced by high applied pressure during specimen preparation showed non-brittle fracture mode due to the fiber pull-out and dutile phases in the matrix.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.71-74
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• 2005

In this paper, the effects of the MWCNTs on the PTC characteristics of the conventional CB/polymer nanocomposites were investigated. For the uniform dispersion of the MWCNTs in the polymer matrix., nitricacid-treated MWCNTs were dispersed with the dissolved HOPE in the solvent. After evaporating solvent, the dried master batches in the oven were melt blended mixed with CB and HDPE to obtain the PTC materials. The initial resistivity of PTC materials decreased and the PTC intensity increased with the MWCNTs. During three repeated heating and cooling cycles, the PTC materials containing MWCNTs showed a great reproducibility due to the conductive network structures of CB particles and MWCNTs.

• Journal of the Korean Society for Railway
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• v.3 no.2
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• pp.92-99
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• 2000

Composites are very useful material for light train carbody due to its high specific strength and lightweight characteristics. The composites, called 3-D board, are developed with a special stitching method. In this process, the glass fiber fabrics of skin material and foam core material are stitched together with glass fiber thread. The glass thread in Z-axis turns into FRP form. The conventional delamination problem can be solved with 3-D sandwich structure. In addition, with the lower density of foam, the weight of the panel and the operation expenses can be highly reduced. To evaluate the usefulness of the 3-D board, the double-deck light train carbody is studied. The stress analyses are carried out under various loads and boundary conditions with FEM Code, ANSYS. On comparing with the aluminum carbody, 3-D board carbody can be reduced by about 2 ton for the total weight of carbody.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.91-94
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• 2003

The purpose of this project is to research and development of thin film supercapacitor with conducting polymer composite electrodes and polymer electrolyte which have high energy density for thin film supercapacitor. We investigated cyclic voltammetry and charge/discharge cycling of PFPT-flyash electrodes. The first discharge capacity of PFPT-flyash electrode with 40wt.% flyash was 24F/g, while that of PFPT-VOflyash electrode with 40wt.% VOflyash was 32F/g. The capacitance of PFPT-VOflyash composite film with polymer electrolyte was 32 F/g at 1st and 20th cycle, respectively. The capacitance of PFPT-VOflyash/Li cell with 40 wt% VOflyash was 141 F/g at 8th cycle.

• Textile Coloration and Finishing
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• v.33 no.4
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• pp.309-316
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• 2021

Due to the rigid nature of the silicon carbide fiber(SiC), fiber damage occurs from the friction during the carding process. This damage not only lowers the spun yarn yield, but also lowers the heat resistance of the spun yarn, so that ultra-high heat resistant yarn cannot be manufactured. Therefore, in the carding process where the most friction between fiber and machine(wire, etc.) occurs, some factors were modified and tested, and as a result of measuring the change in physical properties, fiber damage decreased due to the wire angle or wire density, resulting in improved yield. The test method used to measure the yield of SiC fiber was the carbonization method, and the content of SiC fibers was calculated using the remaining amount after carbonization. Carbonization test was performed at air condition, 700℃, and for 2 hours. Analysis by SEM-EDX showed that the carbide was consistent with the composition of the SiC fiber.

• Elastomers and Composites
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• v.54 no.2
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• pp.97-104
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• 2019

Emulsion styrene-butadiene rubber silica wet masterbatch (ESBR silica WMB) technology was studied to develop highly filled and highly dispersed silica compounds, involving the preparation of a composite by co-coagulating the modified silica and the rubber latex in a liquid phase. Previous studies have shown that when manufacturing ESBR silica WMB/Butadiene silica dry masterbatch (BR silica DMB) blend compounds, preparing BR silica dry masterbatch and mixing it with ESBR silica WMB gave excellent results. However, WMB still has the problem of lower crosslink density due to residual surfactants. Therefore, in this study, tetrabenzylthiuram disulfide (TBzTD) was added instead of diphenyl guanidine (DPG) in the ESBR silica WMB/BR silica DMB blend compounds and sulfur/CBS contents were increased to evaluate their cure characteristics, crosslink densities, mechanical properties, and dynamic viscoelastic properties. TBzTD was found to be more effective in increasing the crosslink density and to produce superior properties compared to DPG. In addition, with increasing sulfur/CBS contents, mechanical properties and rolling resistance were enhanced due to high crosslink density, but the abrasion resistance was not significantly changed because of the toughness.