• Composites Research
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• v.26 no.1
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• pp.72-78
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• 2013

This study explores the resistive heating characteristics of discontinuous carbon fiber (CF)-epoxy composites. Test samples including 1, 3, and 5 wt.% CF were fabricated using sonication and cast molding processes. For heating performance characterization, DC currents were applied to the composite samples, and surface temperatures were evaluated visually and quantitatively using an infrared camera. To estimate the thermal performance of composites and verify the experimental results, finite element analyses were performed. The resistive heating mechanism was investigated in connection with CF loading and applied voltages. Resistive heating efficiency increased proportionately with CF concentration and applied voltage. To obtain homogeneous temperature distribution of the samples, high degree of CF dispersion is required.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.1
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• pp.1-10
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• 2020

This study deals with the fabrication and thermal characterization of planar heating elements attached to the backside of the reflector used in the electrodeless lamp of a freezer. We tried to solve the problem of the local heat generation of the linear heating element that occurs about 50℃. The homogeneous dispersion and manufacturing excellence of the planar heating element produced were confirmed through SEM and EDS. In addition, the test specimens was prepared according to the change in the ratio of carbon fiber to the basis weight of the planar heating element, and a sample having a basis weight of 50g/㎡ having a content ratio of carbon fiber of 70% was selected. That sample showed low surface resistance of 4.3Ω/sq and high temperature of about 81℃ at 6V. Durability was confirmed by performing repeated bending evaluation of 3000 cycles for the sample. Large area test specimens were prepared to be applied to the actual reflector, insulated by EVA film and analyzed for their thermal characteristics. From 13V application, the temperature of the linear heating element was higher than 50℃ and the average temperature of 68℃ was maximum at 18V.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.10
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• pp.1860-1865
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• 2008

40Gbps WDMSystems have been studied by numerical simulation to optimize their performance. Standard single mode fiber is assumed, and the most popular modulation format, NRZ, is used for the study. These assumptions are valid when existing WDM systems are required to upgrade their performance to 40Gbps. It is shown that the standard single mode fiber can transmit optical signals over 4800 (BER < 10-15) by optimizing optical and electrical filter characteristics at the receiver and by compensation of dispersion. In addition, when the system performance is mainly limited by ASE noise of EDFAs, it is found that flattop-shaped optical filter at the receiver gives a better result than Gaussian-shaped filter unless the insertion loss of the optical filter is larger than 5dB.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.198-204
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• 2019

Polymer composites are widely used as industrial materials requiring high mechanical properties. Glass fibers and fillers, which are used as a reinforcement in composites, usually have some problems such as nonuniform dispersion and poor interfacial adhesion. In this study, an acrylic acid-modified polyethylene wax was synthesized by the sequential reaction of pyrolysis of polyethylene followed by grafting with a polar acrylic acid. The acrylic acid-modified polyethylene wax was applied to polymer composites of the polyamide matrix and glass fiber reinforcement. The effect of acrylic acid-modified polyethylene wax on physical properties of polyamide based composites was thoroughly investigated.

• Textile Coloration and Finishing
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• v.33 no.4
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• pp.280-287
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• 2021

Generating electricity by using water in many energy harvesting system is due to their simplicity, sustainability and eco-friendliness. Evaporation-driven moist-electric generators (EMEGs) are an emergent technology and show great potential for harvesting clean energy. In this study, we report a transpiration driven electro kinetic power generator (TEPG) that utilize capillary flow of water in an asymmetrically wetted cotton fabric coated with carbon black. When water droplets encounter this textile EMEG, the water flows spontaneously under capillary action without requiring an external power supply. First carbon black sonicated and dispersed well in three different solvent system such as dimethylformamide (DMF), sodiumdedecylbenzenesulfonate (SDBS-anionic surfactant) and cetyltrimethylammoniumbromide (CTAB-cationic surfactant). A knitted cotton/PET fabric was coated with carbon black by conventional pad method. Cotton/PET fabrics were immersed and stuttered well in these three different systems and then transferred to an autoclave at 120 ℃ for 15 minutes. Cotton/PET fabric treated with carbon black dispersed in DMF solvent generated maximum current up to 5 µA on a small piece of sample (2 µL/min of water can induce constant electric output for more than 286 hours). This study is high value for designing of electric generator to harvest clean energy constantly.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.2
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• pp.152-161
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• 2024

This paper investigates the manufacturing and fundamental quality characteristics of potassium magnesia phosphate-based non-cement high-volume fly ash repair mortar. To derive the optimal mix for non-cement mortar, the manufacturing characteristics were evaluated based on the magnesia ratio, and the mortar manufacturing characteristics were assessed with the fly ash mixture. Additionally, the non-cement magnesia repair mortar was produced considering the effects of fly ash mixture and basalt fiber. The evaluation results determined the optimal mix of non-cement magnesia repair mortar, and the feasibility was examined through workability and fundamental quality assessments. The optimal magnesia ratio was found to be P:M 1:0.5, with W/B at 30 %. It was also confirmed that mixing FA and basalt fiber improves fiber dispersion and workability. Even with over 50 % FA mixture, the target strength was achieved within six hours, with a flow increase of up to 18 % and a flexural strength decrease of about 1-2 MPa.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.753-760
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• 2012

In this study, experimental research was carried out to evaluate and improve the constructability and seismic performance of high strength R/C interior beam-column joints regions, with or without the shear reinforcement, using high ductile fiber-reinforced mortar. Six specimens of retrofitted the beam-column joint regions using high ductile fiber-reinforced mortar are constructed and tested for their retrofit performances. Specimens designed by retrofitting the interior beam-column joint regions (IJNS series) of existing reinforced concrete building showed a stable mode of failure and an increase in load-carrying capacity due to the enhancement of crack dispersion by fiber bridging from using new high ductile materials for retrofitting. Specimens of IJNS series, designed by the retrofitting of high ductile fiber-reinforced mortar in beam-column joint regions increased its maximum load carrying capacity by 96~102.8% and its energy dissipation capacity by 0.99~1.11 folds when compared to standard specimen of SIJC with a displacement ductility of 5.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.102-112
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• 2019

This paper studies impact fracture behavior under temperature variation and compressive flexural strength of cement composites using VAE(vinyl acetate ethylene) powder polymer and PVA(polyvinyl alcohol) fiber. Impact test were conducted in the temperature range selected for the $-35^{\circ}C$, $0^{\circ}C$ and $35^{\circ}C$. In this experimental study, impact test were carried out using a drop impact testing machine (Ceast 9350) to obtain such as displacement, time, and impact fracture energy of normal specimen and and cement composites specimen. As test results, the use of VAE powder polymer and PVA fiber were observed to enhance the flexural strength of mortar. The compressive strength of PVA fibers reinforced cement composites was slightly decreased at 28 days, but the flexural strength was observed to increase 24.4% of normal mortar strength. As a result of the drop impact tests, PVA fiber reinforced cement composites specimens showed microcracks due to energy dispersion and crack prevention with bridge effect of the fibers, and scabbing or perforation by impact was suppressed. On the other hand, the normal mortar and VAE powder polymer cement composites specimens were carried out to the perforation and macro crack. Most of normal mortar and the cement composites subjected to impact load on specimens shows mostly local brittle failure. The impact resistant performance of the specimen with PVA fiber was greatly improved due to the increase of flexure performance.

• ETRI Journal
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• v.32 no.2
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• pp.248-254
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• 2010

We demonstrate a linear bus wavelength-reused gigabit wavelength-division multiplexing passive optical network (WDM-PON) with multiple optical add-drop nodes. A commercially available reflective semiconductor optical amplifier-based WDM-PON has a sufficient power budget to provide multiple optical add/drop nodes in 16 WDM channels. Sixteen 1.25 Gb/s WDM channels are successfully transmitted over 20 km of single-mode fiber with four optical add/drop multiplexers, even with 32 dB reflection and chromatic dispersion in the link.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.27.4-28
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• 2015

The GMT-Consortium Large Earth Finder (G-CLEF) is an optical band echelle spectrograph that has been selected as the first light instrument for the Giant Magellan Telescope (GMT). G-CLEF is a general purpose high dispersion instrument that is fiber-fed and capable of extremely precise radial velocity measurements. G-CLEF has undergone a preliminary design review in April 2015 and is now entering final design phase and construction. G-CLEF has been designed to measure the mass of Earth-analogue exoplanets and to make critical observations in near-field and high-Z cosmology. We describe the G-CLEF instrument and several key science missions that shaped the development of G-CLEF. First light on the GMT is scheduled for late 2020.