• Composites Research
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• v.28 no.5
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• pp.265-269
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• 2015

Development of simple and efficient method for large-scale production of mechanically strong and electrically conductive graphene fiber is highly desirable for practical applications, such as fiber-reinforced composites, wearable electronics, and electromagnetic irradiation shielding. Here, we present a facile approach for the preparation of amine-functionalized graphene fibers by simple wet-spinning of diamine-functionalized graphene oxide (GO-$NH_2$), which is used because of its synthetic convenience, good dispersity, and scalable production with low cost. The amine-functionalized graphene fiber shows high electrical and mechanical properties compared to pristine graphene oxide fiber due to the electrostatic interaction between amine groups and electronegative functional groups of graphene oxide.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.503-506
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• 2013

The shielding coefficient of a conductive length structure is calculated by a ratio of induced voltage with that structure to without that structure. The environments are different between with a structure and without a structure. Beside the corresponding structure, all the parameters related to induced voltage should be normalized to a presumable same environment conditions. Basically each parameter must be compensated, which is a bottom-up type method. In this case, some parameter is not possible to be so because of its unknowing function. Then as a calculated voltage already has all characteristics of parameters, seeking a ratio of calculated induction voltages themselves will include the compensation of all parameters automatically. This is a top-down method.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.13 no.1
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• pp.1-6
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• 2017

In this paper, the flow characteristics of water in the water supply pipes of a WBC array were evaluated. We simulated the flow velocities and pressures for a standard pipe, an expansion pipe with a concentric reducer, and an expansion pipe with an eccentric reducer using computational fluid dynamics. In the case of the standard pipe, when the inlet flow velocities were 0.5 m/s and 2.0 m/s, the maximum flow velocities at the center of the WBC array were 0.54 m/s and 2.74 m/s, respectively, which were the greatest values among those of all the pipe models considered. In the case of the expansion pipe, the maximum flow velocities at the center of the WBC array were almost the same under the same conditions regardless of the type of reducer. The pressure losses in the pipe due to the concentric and eccentric reducers were found to be (165.09 ${\times}$ inlet $velocity^{1.6677}$) and (210.98 ${\times}$ inlet $velocity^{1.6478}$), respectively. The coefficient of determination at this time was greater than 0.99 and was the same for both the models. As a simulation result, it was found that in order to reduce the pressure loss when pipe with WBC array is connected with a conventional pipe, diameter of the pipe with WBC array at that section should be enlarged by one step, and then connected to the conventional pipe with a concentric reducer.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.10
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• pp.118-125
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• 2008

The outages of transmission lines give big damages to the industrial world Lightning outages occupy above 50[%] among the outages of transmission lines. To decrease the lightning outage rates, it is necessary to try countermeasures considering economical points. For the lightning protection of power transmission lines, it is very important to accurately predict the lightning outage rate because the reliability criterion for transmission line is normally specified as the number of flashovers per 100[km] per year. The phenomenon of an insulator flashover by a lightning stroke is a very complex electromagnetic event. And to calculate the lightning outage rates of transmission lines, so many calculation should be repeated because there are many overhead lines and power lines. Therefore it is necessary to develope a program for it. In this paper, we briefly introduce the basic concept for lightning outage calculation algorithm and the program.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1097-1102
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• 2010

Silver coated copper powders were prepared by a chemical reduction method with controlling the deposition process variables such as the feeding rate of the silver ionic solution and concentration of the reductants at room temperature. The characteristics of the products were evaluated by scanning electron microscope (SEM), X-ray diffractometer (XRD), atomic absorption spectrophotometer (AA) and a 4 probe resistivity measurement system. The optimum condition of the preparation of Ag coated Cu powders was at 0.05 M of potassium sodium tartrate and 2 ml/min of the feeding rate of the silver ionic solution. Our method successfully produced dense, uniform, and well-dispersed Ag coated Cu powder of $2{\sim}2.5{\mu}m$ witha silver layer of 100~200 nm. Additionally, we found that thespecific resistivity of the 30 wt.% Ag coated Cu powder was similar to that of pure silver, so that the composite powder could be used as an alternative electromagnetic shielding material for silver.

• Macromolecular Research
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• v.17 no.11
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• pp.863-869
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• 2009

The effect of a multiwalled carbon nanotube (MWCNT) dispersion on the electrical, morphological and rheological properties of polycarbonate (PC)/MWCNT composites was investigated, with and without pretreating the MWCNTs with hydrogen peroxide oxidation and lyophilization. The resulting PC/treated MWCNT composites showed higher electrical conductivity than the PC/untreated MWCNT composites. The morphological behavior indicated the treated composites to have greater dispersion of MWCNTs in the PC matrix. In addition, the electromagnetic interference shielding efficiency (EMI SE) of the treated composites was higher than that of the untreated ones. Rheological studies of the composites showed that the complex viscosity of the treated composites was higher than the untreated ones due to increased dispersion of the MWCNTs in the PC matrix, which is consistent with the electrical conductivity, EMI SE and morphological studies of the treated composites. The latter results suggested that the increased electrical conductivity and EMI SE of the treated composites were mainly due to the increased dispersion of MWCNTs in the PC matrix.

• Journal of the Korean GEO-environmental Society
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• v.12 no.9
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• pp.35-45
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• 2011

This paper is to analyze the behaviors of tunnel support by TDR(Time Domain Reflectometry) sensor using electrical pulse. To analysis the behaviors of tunnel support, Copper tape as sensing materials was studied for on-site installation. Copper tape to the top of the glass tape, foam tape, and shielding the lower part was used electromagnetic shield sheet. For a high sensitivity to load and fill out the measurement noise emissions has been developed for the production of materials. This sensing material through the tunnel model tests for the change by surcharge load in TDR data were analyzed. Varing stiffness and support of conditions were determined the change of TDR data through PVC pipe tunnel section model tests. By comparing TDR data and finite element analysis, the behaviors of the tunnel support materials were analyzed qualitatively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.4
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• pp.556-561
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• 2022

In this paper, we present a block media communication (BMC) system which employs powerline communication to the equipments used in the welding process for ship-assembly and uses metal block as a communication medium. Inductive couplers are installed on digital feeder and pin jig. Information signal is added to the current generated by the welding gun, and applied to the block. When the welding operation starts, information generated in the field is transmitted to the monitoring server in real-time. The field test on the BMC system confirms that the transmitted data are correctly received at the server. Since the proposed system can be built without any changes to the existing welding process, it is helpful to increase competitiveness of the shipbuilding industry through smart factory of shipyards. It is also possible to quickly respond to emergency situations that may occur to workers in an electromagnetic wave shielding environment or a closed space, the effect of preventing industrial accidents will be great.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.1
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• pp.17-33
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• 2022

Ti₃C₂T_X MXene, first reported by Naguib et al. in 2011, has attracted tremendous attention due to its excellent hydrophilicity, electrical conductivity, and mechanical/chemical stability. Since MXene is a two-dimensional material with a thickness of few nanometers, which ensure its flexibility. In last few years, due to these properties many researchers used Ti₃C₂T_X MXene into various fields such as flexible smart sensors, energy harvesting/storage devices, supercapacitors and electromagnetic interference shielding systems. In this review article, we have briefly discussed the various synthesis processes and characteristics of Ti₃C₂T_X MXene. Moreover, we reviewed the latest development of Ti₃C₂T_X MXene as flexible electrode material to be used into different applications.

• Journal of Aerospace System Engineering
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• v.17 no.1
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• pp.68-78
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• 2023

In this paper, improvement measures were studied for false alarm (abnormal lighting) of emergency hydraulic warning light due to RF radiation signals in aircraft. When the warning lamp of the emergency hydraulic system is lit during flight due to electromagnetic interference caused by RF radiation signals, it affects flight mission and safety which can result in efficiency degradation and maintenance of flight mission. For false alarm of emergency hydraulic warning light, root cause analysis and troubleshooting were carried out. By shielding a composite strip under fuselage of the aircraft located in the path of the RF radiation signal, the RF radiation signal flowing into the emergency hydraulic indicator was blocked. Results of applying the improvement method through ground and flight monitoring were also described.