• 한국응용과학기술학회지
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• 제27권2호
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• pp.175-182
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• 2010

Various research on the surface of the skin and the relationship between epidermis and composition of ion have been performed. Traditionally, bamboo extract was used as an important material for enhancing healthy condition of a skin. Bamboo salt is well known as one of the most famous traditional medical treatments. In this study, we investigated the stability of P/S (Polyol-in-Silicone) emulsions containing a fair amount of bamboo salt in the range of 0.5~5.0 wt%. For improving the stability of emulsions, we varied the quantity of fatty alcohol and wax ester in emulsions and the stability was checked using DSC (Differential Scanning Calorimeter). We also studied the efficacy of treating the P/S emulsions containing bamboo salt. From the experiment, the emulsions show the mitigation of stimuli, enhancing the skin hydration and improving the appearance of the skin.

• KIEE International Transactions on Power Engineering
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• 제5A권3호
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• pp.244-251
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• 2005

Power transfer capability has been recently highlighted as a key issue in many utilities. It is determined by the thermal stability, dynamic stability and voltage stability limits of generation and transmission systems. In particular, voltage stability affects power transfer capability to a great extent in many power systems. This paper presents a tool for determining total transfer capability from a static voltage stability viewpoint using IPLAN, which is a high level language used with the PSS/E program. The tool was developed so as to analyze static voltage stability and to determine the total transfer capability between different areas from a static voltage stability viewpoint by tracing stationary behaviors of power systems. A unified power flow controller (UPFC) is applied for enhancing total transfer capability between different areas from the viewpoint of static voltage stability. Evaluation of the total transfer capability of a practical KEPCO power system is performed from the point of view of static voltage stability, and the effect of enhancing the total transfer capability by UPFC is analyzed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.93-95
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• 2002

This paper presents the design of a Unified Power Flow Controller(UPFC) for enhancing the small signal voltage stability in the multi-machine power systems. Recently a lot of attention has been paid to the subject of dynamic stability. The paper deals with analysis of eigenvalue sensitivities with respect to parameters of UPFC Controller. The series branch of the UPFC is designed to damp the power oscillation during transients, while the shunt branch aims at maintaining the bus voltage. Comprehensive time-domain simulation studies using Pss/E show that the proposed robost UPFC controller can enhance the small signal stability efficiently in spite of the variations of power system operating conditions.

• 전기학회논문지
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• 제59권7호
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• pp.1187-1193
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• 2010

This paper provides the methods for enhancing the stability with normal or emergency operating conditions in real power systems and copes with the unbalance of demand of reactive power due to the loss of facility, such as 765kV transmission line. In this paper, we focused on the maximum allowable transmission power(hereafter, MAXTP) in the metropolitan area. In order to increase the MAXTP, the application of reactive power compensators, SVC, and Shunt compensator and reactor, is analyzed as an enhancing method of stability and MAXTP. Particularly, the f-V analysis was performed for the postulated contingency, in order to evaluate the effects on SVC. Conclusively, the stability of power systems could be enhanced and the MAXTP is increased effectively with Dongseoul SVC which has the capacity 200MVAr.

• 한국산학기술학회논문지
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• 제18권12호
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• pp.26-31
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• 2017

전력계통의 과도안정도를 향상시키기 위해 종래에는 무효전력 보상장치를 설치하는 방법을 주로 사용하였다. 전통적인 무효전력 보상장치 중 SVC(Static Var Compensator), 변압기의 탭 변환기는 값이 싸고 기계적 스위칭으로 동작하여 속도가 느리다는 단점이 있고, 전력전자기술을 바탕으로 하는 STATCOM(Static Synchronous Compensator)은 고속으로 동작할 수 있는 장점이 있어 최근에 각광을 받고 있지만 고가의 장치라는 단점이 있다. 또한, 무효전력 보상장치에 기반한 전통적인 방법은 무효전력만을 공급하여 과도안정도를 향상시키기에 대형 전동기의 트립에 의한 급격한 전압붕괴를 막을 수 없다. 반면에 에너지 저장시스템은 무효전력과 유효전력을 동시에 공급할 수 있다. 즉, 선로사고로 인하여 부하에 유효전력의 공급이 감소하는 것을 ESS을 통한 유효전력을 공급함과 동시에 적절한 무효전력의 공급을 통하여 과도안정도를 향상시킬 수 있다. 전력계통의 사고 시 유효전력의 빠른 공급은 과도안정도 향상에 매우 중요한 역할을 한다. 본 논문에서는 대형 전동기 부하와 같은 큰 동적부하를 가지는 전력계통에 대하여 에너지저장시스템을 사용한 과도안정도 향상방법을 제시한다. 또한, 유효전력과 무효전력을 보상하는 방법이 기존의 방법보다 더 효과적으로 과도안정도를 향상시킴을 확인하였다.

• 한국재료학회지
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• 제32권11호
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• pp.474-480
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• 2022

Lithium-ion batteries (LIBs) are powerful energy storage devices with several advantages, including high energy density, large voltage window, high cycling stability, and eco-friendliness. However, demand for ultrafast charge/discharge performance is increasing, and many improvements are needed in the electrode which contains the carbon-based active material. Among LIB electrode components, the conductive additive plays an important role, connecting the active materials and enhancing charge transfer within the electrode. This impacts electrical and ionic conductivity, electrical resistance, and the density of the electrode. Therefore, to increase ultrafast cycling performance by enhancing the electrical conductivity and density of the electrode, we complexed Ketjen black and graphene and applied conductive agents. This electrode, with the composite conductive additives, exhibited high electrical conductivity (12.11 S/cm), excellent high-rate performance (28.6 mAh/g at current density of 3,000 mA/g), and great long-term cycling stability at high current density (88.7 % after 500 cycles at current density of 3,000 mA/g). This excellent high-rate performance with cycling stability is attributed to the increased electrical conductivity, due to the increased amount of graphene, which has high intrinsic electrical conductivity, and the high density of the electrode.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.151-153
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• 2002

Using UPFC(Unified Power Flow Controlled), it is possible to control three parameters(voltage, impedance, and phase angle). The UPFC can generate or absorb reactive power rapidly so as to enhance the transient and voltage stability and also influence the power flow. In this paper, the effects of application of the UPFC to the power system are analyzed from a viewpoint of improving the total transfer capability by enhancing voltage stability. The IPLAN, which is a high level language used with PSS/E program, is employed for evaluating the total transfer capability from a f-V curve.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 춘계학술발표회요약집
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• pp.168-168
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• 2001

• Journal of Electrochemical Science and Technology
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• 제15권1호
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• pp.96-110
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• 2024

Polymer electrolyte membrane fuel cells (PEMFCs) are green energy conversion devices, for which commercial markets have been established, owing to their application in fuel cell vehicles (FCVs). Development of cathode electrocatalysts, replacing commercial Pt/C, plays a crucial role in factors such as cost reduction, high performance, and durability in FCVs. PtNi octahedral catalysts are promising for oxygen reduction reactions owing to their significantly higher mass activity (10-15 times) than that of Pt/C; however, their application in membrane electrode assemblies (MEAs) is challenged by their low stability. To overcome this durability issue, various approaches, such as third-metal doping, composition control, halide treatment, formation of a Pt layer, annealing treatment, and size control, have been explored and have shown promising improvements in stability in rotating disk electrode (RDE) testing. In this review, we aimed to compare the features of each strategy in terms of enhancing stability by introducing a stability improvement factor for a direct and reasonable comparison. The limitations of each strategy for enhancing stability of PtNi octahedral are also described. This review can serve as a valuable guide for the development of strategies to enhance the durability of octahedral PtNi.

• 한국자동차공학회논문집
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• 제18권6호
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• pp.105-113
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• 2010

In this study, a feasibility test of liquid petroleum gas (LPG) compression ignition (CI) engine has been carried out to study the effectiveness of cetane enhancing additive: Di-tertiary-butyl peroxide (DTBP). Performance and emissions characteristics of a CI engine fuelled with DTBP blended LPG fuel were examined. Also, the effect of EGR (exhaust gas recirculation) on the combustion and emissions characteristics has been investigated. Results showed that stable engine operation over a wide range of the engine loads was possible. Exhaust emissions measurements showed that hydrocarbon were decreased with the blended fuel at enhancing cetane number. Furthermore, the combustion stability of LPG with a cetane number improver was equivalent to that of commercial Diesel fuel. Increasing the EGR rate leads to deteriorate the IMEP (indicated mean effective pressure) and increase the ignition delay. It was found that the exhaust emissions with the EGR resulted in a very large reduction in nitrogen oxides at the expense of higher THC and CO emissions. Considering the results of engine performance and exhaust emissions, LPG blended fuel of enhancing cetane number could be used as an alternative fuel for diesel in a CI engine.