• Journal of Electrochemical Science and Technology
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• 제1권1호
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• pp.63-68
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• 2010

The $Li_4Ti_5O_{12}$/AC composite was prepared by sol-gel process with ultrasonication. The prepared composite was characterized by SEM, XRD and TG analysis, and their electrochemical behaviors were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge test in 1M $LiBF_4$/PC electrolyte. From the results, the $Li_4Ti_5O_{12}$ particles coated on AC surface had an average particle size of 100 nm and showed spinel-framework structure. When the potential range of the $Li_4Ti_5O_{12}$/AC composite was extended from 0.1 to 2.5 V, redox peaks and electric double layer property were revealed. The initial discharge capacity of $Li_4Ti_5O_{12}$/AC composite was 218 mAh $g^{-1}$ at 1 C. The enhancement of discharge capacity was attributed to electric double layer of added activated carbon.

• 한국수소및신에너지학회논문집
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• 제31권2호
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• pp.242-249
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• 2020

The Kalina cycle (KC) is considered as one of the most efficient systems for recovery of low grade heat. Recently, Kalina based power and cooling cogeneration cycles (KPCCCs) have been suggested and attracted much attention. This paper presents an energy and exergy analysis of a recently suggested KPCCC with flexible loads. The cycle consists of a KC (KCS-11) and an aqua-ammonia absorption refrigeration cycle. By adjusting the splitting ratios, the cycle can be operated with four modes of pure Kalina cycle, pure absorption cooling cycle, Kalina-cooling parallel cycle, and Kalina-cooling series cycle. The effects of system variables and the operating modes on the energetic and exergetic performances of the system are parametrically investigated. Results show that the system has great potential for efficient utilization of low-grade heat source by adjusting loads of power and cooling.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.328-328
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• 2007

$SnO_2$ has a high potential for electric and electronic applications. We have anodized pure tin metal and nano porous tin oxide film was obtained on pure Sn. Nano porous tin oxide were grown by anodization in nonaqueous-base electrolytes at different potentials between 5 V and 100 V. Pore size of ~100nm was observed by FE-SEM. Pore sizes as a function of applied voltage and anodizing time were characterized. We obtained nano porous tin oxide film having an uniform pore size at low temperature. High specific surface area of $SnO_2$ will be very useful for gas sensor, lithium battery, and dye sensitized solar cell.

• Journal of Electrochemical Science and Technology
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• 제12권3호
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• pp.317-322
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• 2021

Silicon (Si) has been considered as a promising anode material because of its abundant reserves in nature, low lithium ion (Li⁺) intercalation/de-intercalation potential (below 0.5 V vs. Li/Li⁺) and high theoretical capacity of 4200 mA h/g. In this paper, we prepared a silicon-based (Si-based) anode material containing a small amount of silicon carbide by using magnesiothermic coreduction of silica and hexachlorobenzene. Because of good conductivity of silicon carbide, the cycle performance of the silicon-based anode materials containing few silicon carbide is greatly improved compared with pure silicon. The raw materials were formulated according to a silicon-carbon molar ratio of 10:0, 10:1, 10:2 and 10:3, and the obtained products were purified and tested for their electrochemical properties. After 1000 cycles, the specific capacities of the materials with silicon-carbon molar ratios of 10:0, 10:1, 10:2 and 10:3 were still up to 412.3 mA h/g, 970.3 mA h/g, 875.0 mA h/g and 788.6 mA h/g, respectively. Although most of the added carbon reacted with silicon to form silicon carbide, because of the good conductivity of silicon carbide, the cycle performance of silicon-based anode materials was significantly better than that of pure silicon.

• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.156-163
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• 2018

High-performance mixed-matrix membranes that comprise both zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were synthesized with a solution casting technique to realize excellent $CO_2/CH_4$ separation. The incorporation of ZIF-8 nanocrystals alone in ODPA-TMPDA polyimide can be used to significantly enhance $CO_2$ permeability compared with that of pure ODPA-TMPDA. Meanwhile, the addition of a GO nanostack alone in ODPA-TMPDA contributes to improved $CO_2/CH_4$ selectivity. Hence, a composite membrane that contains both fillers displays significant enhancements in $CO_2$ permeability (up to 60%) and $CO_2/CH_4$ selectivity (up to 28%) compared with those of pure polymeric membrane. Furthermore, in contrast to the ZIF-8 mixed-matrix membrane, which showed decreased mechanical stability, it was found that the incorporation of GO could improve the mechanical strength of mixed-matrix membranes. Overall, the synergistic effects of the use of both fillers together are successfully demonstrated in this paper. Such significant improvements in the mixed-matrix membrane's $CO_2/CH_4$ separation performance and mechanical strength suggest a feasible and effective approach for potential biogas upgrading and natural gas purification.

• 마이크로전자및패키징학회지
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• 제11권3호
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• pp.55-62
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• 2004

여러 가지 온도와 습도에 따라 Sn의 표면에 형성되는 산화물을 전기화학적 환원방법을 이용해 분석하였다. 전기화학적 방법을 이용하여 금속표면에 형성된 산화물을 환원시킬 때 나타나는 환원전위와 소모된 전하량을 측정하여 표면 산화물의 종류와 양을 정량적으로 분석하였다 우선 전기화학적 환원 방법이 금속 표면 산화물의 분석에 적합한지 알아보기 위해 여러 가지 산화물 분말의 환원 전위와 수소 발생 전위를 측정하였고, 분석을 위한 최적의 전류밀도 값을 구하였다. Sn 표면에 생성된 산화물을 분석한 결과 $85^{\circ}C$의 건조한 환경에서 보다 T/H (Temperature/Humidity, $85^{\circ}C$/$85\%$상대습도)조건에서 SnO가 더 빠르게 성장하였다. 또한 T/H 조건에서 하루가 지난 이후부터는 Sn의 표면 최상층에 매우 얇은 (<10 ${\AA}$) $SnO_2$ 가 형성되어 있는 것을 확인하였다. $150^{\circ}C$에서는 SnO와 $SnO_2$가 같이 존재하는 것을 확인하였다. 또한 XPS와 AES 표면분석을 통하여 환원 실험 결과를 뒷받침하였다.

• KSBB Journal
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• 제26권3호
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• pp.223-228
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• 2011

The effects of pH, glycerol concentration and salt on cell growth and ethanol production using Enterobacter aerogenes KCTC 2190 were evaluated in the anaerobic culture condition. In condition of initial pH 5, cell growth and ethanol production were highest. An initial concentration of 10 g/L of pure glycerol gave the highest cell growth and ethanol production. However, in case of over 15 g/L of pure glycerol, they decreased. The cell growth and ethanol production decreased with the increase of salt concentration. When 10 g/L of crude glycerol was used as the carbon source, the cell growth and ethanol production were $1.32\;OD_{600}$ and 3.95 g/L, respectively, which were about 94.4% and 88.5% compared to those of pure glycerol. These result indicates that the crude glycerol produced in the biodiesel manufacturing process maybe useful as a potential carbon source for ethanol production form Enterobacter aerogenes KCTC 2190.

• 농촌지도와개발
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• 제9권2호
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• pp.263-277
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• 2002

The objective of this study was to compare the farm efficiency of members of cooperative firms with that of non-members in Korea. Data were collected from 27 farms members of three cooperatives and 13 non-member farms, based on the managerial achievements of 1999. For the analysis, the data were divided into three different farming types: type I and II of member farms and non-member farms. Economic analysis were implemented using DEA(Data Envelopment Analysis). Major findings was as follows. Total average technology efficiency was 0.782, which implies that there still remains 21.8% of improvement possibility. Among the three types, type I showed the highest technology efficiency of 0.9055, while type II and non-member farms showed 0.7670 and 0.7171, respectively. This means that these farms have relatively high potential improved. Also, comparing technology efficiency by dividing into pure technology and scale efficiency, all type of the farms exhibit a higher pure technology efficiency compared to scale efficiency. Therefore, to improve current technology efficiency, farms need to focus more on pure technology efficiency improvement. Meanwhile, profit analysis based on farm size indicate that most of the farms demonstrated the increasing-return-to-scale, which means it is necessary to extend the farm size to improve technical efficiency. Type I member farms achieve higher profit and efficiency than other two types and relatively higher producer prices through introducing cooperative sorting, grading and packing. Also, these labor saving technologies increased farm size.

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.383-388
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• 1994

일정한 단속 주파수(triggering frequency)를 지닌 청각자극의 반송 주파수(carrier ferquency, pure tone)를 1kHz에서 3kHz까지 0.5kHz단위로 증가시키면서, 이에 반응하는 뇌전위를 디지탈 EEG측정장치를 이용하여 총 7초 동안 1kHz의 sampling frequency로 컴퓨터로 전송하였다. 먼저 신호의 pseudo-phase space분석을 통해 뇌전위의 진폭특성을 파악하였다. 이러한 해석은 생리학적으로 밝져진 소리의 반송주파수와 소리의 크기 인지사이의 상관관계와 잘 일치함이 확인되었다. 또한 이 신호외 Lyapunov exponent 분석을 통해 신호의 발산 특성을 물리적으로 파악하고, 이러한 특성을 이미 여러가지 접근법에 의해 밝혀져 있는 생리학적 실험결과와 관련지어 해석함으로써 반송 주파수에 반응하는 뇌의 mechanism을 뇌전위 측정에 의해서 검출이 가능함을 확인할 수 있었다.

• Membrane and Water Treatment
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• 제6권1호
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• pp.1-13
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• 2015

The modification of ultrafiltration membranes with carbon nanotube (CNT) buckypaper on fouling control was investigated. Two types of commercially available flat-sheet membranes were used: PS35 and PES900C/D (PES) (the PS35 membranes were hydrophilic with a molecular weight cutoff of 20 kDa, and the PES membranes were hydrophobic with a molecular weight cutoff of 20 kDa). The CNT buckypaper modified ultrafiltration membranes were prepared by filtering a CNT suspension through the flat-sheet membrane in a dead-end ultrafiltration unit. After modification, the pure water flux of PES was significantly increased, while the pure water flux of PS35 was decreased. The properties of the CNT modified membranes were also investigated. Considering the antifouling properties, pure water flux of the modified membrane, and the stability of CNT buckypaper layer on the membrane surface, ethanol solution with a concentration of 50 wt.%, multi-walled carbon nanotubes (MWCNTs) with a larger diameter (30-50 nm), and the CNT loading with $7.5g/m^2$ was selected. The CNT buckypaper on the surface of ultrafiltration membranes can trap the pollutants in sewage effluent and prevent them reaching the surface of virgin membranes. Water quality analysis showed that the effluent quality of the modified membrane was obviously improved. The removal efficiency of humic acid and protein-like matters by the modified membrane was significant. These results indicate the potential application of the CNT buckypaper layer modified membranes in the field of wastewater reclaim.