• Journal of the Korean Electrochemical Society
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• v.14 no.4
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• pp.239-244
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• 2011

In this study, $Fe_3O_4$/graphene and CuO/graphene composites were synthesized by the polyol reduction method using ethylene glycol, and their performances as the anodes of lithium ion batteries were evaluated. The physical characteristics of the synthesized composites were analyzed by SEM, XRD, and TGA. In addition, their electrochemical properties were examined by the electrochemical analysis techniques such as charge/discharge performance, cyclic voltammetry, and AC impedance spectroscopy. The cells composed of $Fe_3O_4$/graphene and CuO/graphene composites showed better performance than the graphene electrode, due to the dispersion of nanosized $Fe_3O_4$ or CuO on the surface of graphene and the formation of good electrical network in the electrode. Their composites kept the reversible capacity more than 600 mAh/g even after the charging/discharging of 30 cycles.

• Journal of IKEEE
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• v.23 no.4
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• pp.1230-1235
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• 2019

In this paper, we have developed sensor composited heater of 2-pin, and unified the fuel filter. In order to evaluate the performance of the 2-pin sensor composited fuel heater, we have make of the low temperature fluidity system. The one measure and analysis the electrical and oil flow quantity characteristics at an input and out port of 2-pin sensor composited fuel heater. Especially, in the characteristics verification elements of the proposed goods, we use the test chamber for the temperature variable and oil flow quantity test, and designed an embedded system for interfacing an engine. By interfacing both user and the system, it support an experimental and date gathering function in 2-pin sensor composited fuel filter. And then test the temperature, oil pressure, electrical characteristics and oil flow quantity in variable status from - 30 ℃ to + 80 ℃. These can help us to determine the quality and performance of elementary goods.

• Journal of Navigation and Port Research
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• v.37 no.3
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• pp.257-262
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• 2013

A ship operating in rough sea may suffer from an undesirable motion which may severely degrade the performance of equipment onboard and give a person an uncomfortable feeling. Hence, roll stabilization received a considerable attention and various devices including bilge keels, stabilizing fins, gyroscopic, anti-rolling tanks, rudders and flaps have been conceived and utilized for the purpose. The Coanda effect is evident when a jet stream is applied tangential to a curved surface of a hydrofoil since then the jet increases the circulation around the foil and consequently the lift. Model tests and numerical simulation have been conducted to examine the practicality of a fixed type fin stabilizer augmented by the Coanda jet. The results show that the lift coefficient of the modified Coanda fin at the zero angle of attack identically coincides with that of the original fin at ${\alpha}=\26^{\circ}$ when Coanda jet is supplied at the rate of $C_j$ = 0.25. It is also shown that fixed type fin stabilizers for active control of the motions of ships and the other mobile units without rotation can be put to practical use if the Coanda effect is applied.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.135-141
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• 2020

Although the graphene is regarded as a promising material for the electrode of the supercapacitor, its electrochemical performance is still less enough to satisfy the current demand raised in real applications. Here, using a home laser engraver, firstly we performed the prompt and selective reduction of the graphene oxide to produce multilayered and highly porous graphene maintaining high electrical conductivity. Subsequently, the resulting graphene was conformally deposited with pseudocapacitive thin VO_x using atomic layer deposition in order to enhance specific capacitance of graphene. We observed that various forms of VO_x exist in the VO_x/graphene hybrid through XPS analysis. The hybrid showed highly improved specific capacitance (~189 F/g) as compared to the graphene without VO_x. We expect that our approach is accepted as one of the alternatives to produce the graphene-based electrode for various energy storage devices.

• Membrane Journal
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• v.32 no.6
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• pp.411-426
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• 2022

Energy plays a significant role in modern lifestyle because of our extensive reliance over energy-operating devices. Therefore, there is a need for alternative and green energy resources that can fulfill the energy demand. For this, fuel cell (FCs) especially anion exchange membrane fuel cells (AEMFCs) have gained tremendous attention over the other (FCs) due to their fast reaction kinetics without using noble catalyst and allow to use of cheaper polymers with high performance. But lack of highly conductive, chemically, and mechanically stable anion exchange membrane (AEM) still main obstacle to the development of high performance AEMFCs. Therefore, graphene-based polymer composite membranes came into the existence as AEMs for the FCs. The exceptional properties of the graphene help to improve the performance of AEMs. Still, there are lot of challenges in the graphene derivatives based AEMs because of their high tendency of agglomeration in polymer matrix which reduced their potential. To overcome this issue surface modification of graphene derivatives is necessary to restrict their agglomeration and conserved their potential features that can help to improve the performance of AEM. Therefore, this review focus on the surface modification of graphene derivatives and their role in the fabrication of AEMs for the FCs.

• Korean Journal of Optics and Photonics
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• v.25 no.6
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• pp.311-314
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• 2014

In this paper, we design a helical fin structure for the heat sink for a high-power LED lighting module, and analyze its thermal properties. By means of the helical fin structure, we can obtain about 14% larger surface area for the limited volume and it can decrease the LED chip temperature by about 12%. Because this helical fin heat sink has 15% less total volume than a conventional one, we can also expect to reduce the production cost due to these structural properties.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.89.1-89.1
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• 2012

실리콘 반도체의 Ultra large scale integration (ULSI) 기술 및 소자의 나노스케일화에 따라 배선 금속 물질로 사용하던 알루미늄 보다 낮은 비저항을 가지면서 금속의 전자이동효과에 잘 견딜 수 있는 차세대 배선 물질로서 구리가 큰 주목을 받고 있다. 하지만 구리의 경우, 높은 확산성을 가지기 때문에 열처리 과정에서 구리 실리사이드가 형성되는 등 소자의 신뢰성 및 성능을 감소시키므로, 이를 방지하기 위한 확산 방지막이 필요하다. IC의 배선에서 사용되는 기존의 확산 방지막은 Ta, TaN, TiN, TiW, TaSiN 등으로, 대부분 금속으로 이루어져 있기 때문에 증착 장비를 이용하여 두께를 조절하는 기술, 박막의 질을 최적화 하는 과정이 필요하며, 증착 과정 중에서 불순물이 함께 증착되거나 실리사이드가 형성되는 등의 단점을 가진다. 구리 기반의 배선 물질에서 문제될 수 있는 또 한가지의 이슈는 소자의 나노스케일화에 따른 배선 선폭의 감소로 인하여 확산 방지막 두께 또한 감소되어야 하는 것으로서, 확산 방지막의 두께가 감소함에 따른 방지막의 균일성 감소, 연속성 등이 큰 문제로 작용할 수 있어 이를 해결하기 위한 새로운 기술 또는 새로운 확산 방지막 물질의 개발이 시급한 실정이다. 본 연구에서는 구리/실리콘 구조에서 금속의 실리콘 박막 내로의 확산 및 실리사이드 형성을 방지하기 위하여 그래핀을 확산 보호막으로서 사용하였다. 그래핀은 화학기상증착법을 이용하여 한 겹에서 수 겹으로 성장되었으며, PMMA 물질을 이용하여 실리콘 기판에 전사되었다. 구리/그래핀/실리콘 구조의 샘플을 500 ~ 800도의 온도 범위에서 열처리 하였고, 구리 실리사이드 형성 여부를 XRD로 분석하였다. 또한 TEM 분석을 통해 구리 실리사이드의 형성 모양을 관측하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.10
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• pp.781-785
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• 2002

The effects of different surfaces on dry and wet frosting test were experimentally investigated. The results of experiment were compared by the performance evaluation coefficient (PEC). Results showed that the air-side pressure drop of lacquer coated evaporator increased by 5% as compared to the plasma treated one. It was also found that the Plasma coated evaporator is lower than lacquer coated one in the PEC ratio.

• Journal of Energy Engineering
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• v.16 no.1 s.49
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• pp.7-14
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• 2007

An experimental study is performed to investigate the effect of air-side heat transfer and friction on characteristics of finned tube heat exchanger under dry surface and wet surface conditions (RH 50%, 70%). Air enthalpy calorimeter is used to obtain the performance evaluation and analysis of a fined tube heat exchanger. Four finned tube heat exchangers with slit fin or plain fin are tested. The number of tube rows are 2 and 3, and the tube diameter is 7 mm. Air-side heat transfer and friction are presented in terms of j factor and friction factor. At dry surface condition, j factor decreases with increasing Re and j factor of 3 row is lower than that of 2 row. Also, the friction factor of a slit fin is larger than that of a plain fin. At wet surface condition, the heat transfer effect is more significant in the case of the slit fin than the plain fin and 2 row than 3 row. The j factor and friction factor are affected by humidity, tube row and fin configuration.

• Composites Research
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• v.36 no.5
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• pp.342-348
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• 2023

There has been increasing demand for real-time monitoring of body and ambient temperatures using wearable devices. Graphene-based thermistors have been developed for high-performance flexible temperature sensors. In this study, the temperature coefficient of resistance (TCR) of monolayer graphene was controlled by coating polyethylenimine (PEI) on graphene surfaces to enhance its temperature-sensing performances. Monolayer graphene grown by chemical vapor deposition (CVD) was wet-transferred onto a target substrate. To facilitate the interfacial doping by PEI, the hydrophobic graphene surface was altered to be hydrophilic by oxygen plasma treatments while minimizing defect generation. The effect of PEI doping on graphene was confirmed using a back-gated field-effect transistor (FET). The CVD-grown monolayer graphene coated with PEI exhibited an improved TCR of -0.49(±0.03) %/K in a temperature range of 30~50℃.