• Steel and Composite Structures
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• v.32 no.1
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• pp.59-66
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• 2019

Hollow steel-reinforced concrete-filled GFRP tubular member is a new kind of composite members. Firstly set the mold in the GFRP tube (non-bearing component), then set the longitudinal reinforcements with stirrups (steel reinforcement cage) between the GFRP tube and the mold, and filled the concrete between them. Through the axial compression test of the hollow steel-reinforced concrete-filled GFRP tubular member, the working mechanism and failure modes of composite members were obtained. Based on the experiment, when the load reached the ranges of $55-70%P_u$ ($P_u-ultimate$ load), white cracks appeared on the surface of the GFRP tubes of specimens. At that time, the confinement effects of the GFRP tubes on core concrete were obvious. Keep loading, the ranges of white cracks were expanding, and the confinement effects increased proportionally. In addition, the damages of specimens, which were accompanied with great noise, were marked by fiber breaking and resin cracking on the surface of GFRP tubes, also accompanied with concrete crushing. The bearing capacity of the axially compressed components increased with the increase of reinforcement ratio, and decreased with the increase of hollow ratio. When the reinforcement ratio was increased from 0 to 4.30%, the bearing capacity was increased by about 23%. When the diameter of hollow part was decreased from 55mm to 0, the bearing capacity was increased by about 32%.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.49-53
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• 2006

This paper specifies the new power supply paradigm converting 154kV voltage level into 22.9kV class with equivalent capacity using superconducting rower facilities and analyze the fault current characteristics with and without HTS-FCL (High Temperature Superconducting-Fault Current Limiter). Superconducting new power system is the power system to which applies the 22.9kV HTS cable in parallel to HTS transformer and HTS-FCL with low-voltage and mass-capacity characteristics replacing 154kV conventional cable and transformer. The fault current of superconducting new power system will increase greatly because of the mass capacity and low impedance of HTS transformer and cable. This means that the HTS-FCL is necessary to reduce the fault current below the breaking current of circuit breaker. This paper analyze the fault current and suggests the parallel HTS-FCL scheme complementing the inherent problem of HTS-FCL, that is recovery after quenching is impossible within shorter than a few seconds.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.5
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• pp.644-650
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• 2018

According to a miniaturization and integration of electric device, a little size of fuse satisfying the current carrying capacity as well as an explosive tolerance and current interrupt rating are required. Fe-Ni alloy is applied to decrease an oxidation of fuse elements. A resistance and T.C.R(temperature coefficient of resistance) of a fuse are analyzed by changing a content of Ni And full rated current I-T curve from 1A to 6.3A has been tested. In order to an explosive energy, a straight wire type is selected to reduce a fuse melting time. An interrupt rating test was conducted by changing a content of Ni and the optimal content of Ni is to be 40%.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.2
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• pp.315-320
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• 2012

Generally circuit devices of low voltage are as follows, ICCB, PCB and MCCB. Among them, MCCB is typically used because it has superior characteristics which fuses do not possess, such as safety, controllability and ability to collaborate with other devices. The MCCB plays vital role, it has to trip instantaneously when the fault is occurred as well as it must have high insulation capacity. Therefore in order to enhance the breaking capacity, the study of contact construction, contact tip and link are necessary. This paper shows dynamic modeling of mechanism part of MCCB using an exclusive analysis program, and embodies the research of improvement of mechanism performance.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.438-442
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• 2006

The degradation of Nafion membrane by hydrogen peroxide was investigated in polymer electrolyte membrane fuel cell (PEMFC). Degradation tests were carried out in a solution of $10{\sim}30%$ hydrogen peroxide containing 4ppm $Fe^{2+}$ ion which is well known as Fenton's reagent at $80^{\circ}C$ for 48hr. Characterization of degraded membranes were examined through the IR, Water-uptake, Ion exchange capacity, mechanical strength and $H_2$ permeability. After degradation, C-F, S-O and C-O chemical bonds of membrane were broken by radical formed by $H_2O_2$ decomposition. Breaking of C-F bond which is the membrane backbone reduced the mechanical strength of Nafion membrane and hence induced pinholes, resulting in increase of $H_2$ crossover through the membrane. Also the decomposition of C-O and S-O, side chain and terminal bond of membrane, decreased the ion exchange capacity of the membrane.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.4
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• pp.149-153
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• 2005

We have investigated thermal properties showed by changing the content of carbon black which is the component parts of semiconductive shield in underground power transmission cable. Specimens were made of sheet with the nine of those for measurement. Heat capacity (${\Delta}$H), glass transition temperature (Tg) and melting temperature (Tm) were measured by DSC (Differential Scanning Calorimetry). The ranges of measurement temperature were from -100($^{\circ}C$) to 100($^{\circ}C$), and heating rate was 4($^{\circ}C$/min). And then thermal diffusivity was measured by LFA 447. The dimension of measurement temperature was 25[$^{\circ}C$]. Glass transition temperature of specimens was showed near -25[$^{\circ}C$] and the heat capacity and the melting temperature from the DSC results were simultaneously decreased according to increasing the content of carbon black, while thermal diffusivity was increased according to increasing the content of carbon black. Because ionic impurities of carbon black having Fe, Co, Mn, Al and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.160.2-160.2
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• 2014

Recently silicon has attracted intense interest as a promising anode material of lithium-ion batteries due to its extremely high capacity of 4200 mA/g (for Li4.2Si) that is much higher than 372 mAh/g (for LiC6) of graphite. However, it seriously suffers from large volume change (even up to 300%) of the electrode upon lithiation, leading to its pulverization or mechanical failure during lithiation/delithiation processes and the rapid capacity fading. To overcome this problem, Si nanowires have been considered. Use of such Si nanowires provides their facile relaxation during lithiation/delithiation without mechanical breaking. To design better Si electrodes, a study to unveil atomic-scale mechanisms involving the volume expansion and the phase transformation upon lithiation is critical. In order to investigate the lithiation mechanism in Si nanowires, we have developed a reactive force field (ReaxFF) for Si-Li systems based on density functional theory calculations. The ReaxFF method provides a highly transferable simulation method for atomistic scale simulation on chemical reactions at the nanosecond and nanometer scale. Molecular dynamics (MD) simulations with the ReaxFF reproduces well experimental anisotropic volume expansion of Si nanowires during lithiation and diffusion behaviors of lithium atoms, indicating that it would be definitely helpful to investigate lithiation mechanism of Si electrodes and then design new Si electrodes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.327-332
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• 2019

Recently, inverter control systems have attracted immense attention to increase the energy efficiency. However, such systems use repeated on/off high currents for linear operation control, instead of the prevalent step variable current control method. Hence, there arise concerns of personal and property damage, especially due to the durability, explosive characteristics, and operating speed of the fuse, which is responsible for safety and is one of the internal components using current control. Therefore, in this paper, we propose an IEC60127-4 SMD sub-miniature fuse, consisting of Ag-Cu alloys and ceramic powder for arc soothing. The IEC60127-4 SMD sub-miniature fuse has high durability and cut-off capacity, and operates safely in dangerous circumstances caused by the inverter control system.

• Journal of the East Asian Society of Dietary Life
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• v.17 no.3
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• pp.393-401
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• 2007

This study was performed to investigate the antioxidant activity of Korean ginseng using an ORAC(Oxygen Radical Absorbance Capacity) assay. Four fractions each (80% ethanol, ethyl acetate, water saturated 1-butanol, and water) were obtained from different ginseng samples (White Ginseng: ; 6 yrs-., 5 yrs-., ; Cork Ginseng: ; 5 yrs-., 4 yrs-.). The saponin content of each fraction was quantified by LC/MS, and the antioxidant capacity of the ginseng was measured by the ORAC assay. The ORAC method, which was recently validated using automatic liquid handling systems, has been adapted for manual handling with the use of a conventional fluorescence microplate reader. Furthermore, the ORAC assay provides a direct measure of hydrophilic chain-breaking antioxidant capacity against peroxy radical, which is the exiting and emission of 2,2'-Azobis (2-methylpropionamidine)-dihychloride (AAPH). As a result of our experiments, ginsenosides Rg1 and Rb1 were the two major saponins found in the ginseng samples, and Rc, Rb2, Re, Rd, Rg3, and Rh1 were detected in a small quantities. For the antioxidant capacities of the fractions (80% ethanol, ethyl acetate, butanol, and water), we found that the organic solvent fraction had similar antioxidant capacities, and were higher than the capacity of the water fraction. When determining the similarities in each fraction, only the ethyl acetate fraction showed similarity compared to other fractions (p>0.05). The antioxidant capacity of ginseng may come from phenolic compounds and some nonpolar saponins. However, based on the results of this study, we hypothesize that some acidic polysaccharides and other biological components may contribute to its antioxidant capacity. Additional research is required to determine other possible biological response modifiers that contribute to the antioxidant capacity of ginseng.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.770-774
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• 2003

The effects of pH and/or NaCl concentration on the Fat Binding Capacity (FBC) of rhamnolipid and the physical properties of surimi gel containing rhamnolipid were investigated. The FBC of rhamnolipid was measured 162% of value at pH 7 and 0% NaCl concentration. The whiteness of surimi gel containing rhamnolipid significantly (p< 0.05) lower than control. In contrast, surimi gel containing rhamnolipid compare with control were enhanced significantly(p < 0.05) breaking force and deformation.