• Journal of the Korean Wood Science and Technology
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• 제40권2호
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• pp.71-77
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• 2012

Cellulose nanowhisker (CNW) isolated from hardwood bleached kraft pulp (HW-BKP) using sulfuric acid hydrolysis was suspended in polyvinyl alcohol (PVA) and electrospun into composites nanofibers. Transmission electron microscopy (TEM) revealed the CNW to be rod-like, approximately of $16.1{\pm}4.6$ nm wide and $194{\pm}61$ nm long, providing an aspect ratio of about 12, with a particle size distribution range of $662.2{\pm}301.2$ nm. Uniform and high quality CNW/PVA composite nanofibers were successfully manufactured by the electrospinning method. As the CNW loading increases, the viscosity of CNW/PVA solutions shows a minimum at 1% CNW level which subsequently results in the smallest diameter (193 nm) of electrospun nanofibers. The average diameter of the nanofibers increased up to 284 nm with increasing CNW loading. These results suggest that the electrospinning method provides a great potential of manufacturing consistent and reliable nanofibers from CNW/PVA solution for the formation of scaffolds with potentials in future application.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.453.2-453.2
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• 2014

그래핀을 수직으로 성장한 형태인 탄소나노월(Carbon nanowall; CNW)은 탄소를 바탕으로 하는 다른 나노물질에 비해 표면적이 상당히 넓은 물질로 전극에 활용하여 소자 성능향상을 기대 할 수 있다. 또한 탄소를 기반으로 하는 나노 구조물중에서 가장 높은 표면밀도를 가진다. CNW를 차세대 염료감응형 태양전지(Dye sensitised solar cells; DSSC)의 상대전극으로 사용한다면 기존대비 광변환 효율을 향상시킬 수 있어 새로운 상대전극으로 활용 가능하다. 또한 CNW는 다른 촉매 없이 직접성장이 가능함으로 불순물 제거공정이 필요하지 않고, 공정시간이 짧아 대량생산에 용의하다. 본 연구에서는 마이크로웨이브 PECVD 장비를 사용하고 메탄(CH4)을 반응가스로 사용하여 CNW 하부전극을 제조하였다. CNW 하부전극의 광 변환효율을 관찰하기위해서 합성시간을 변화를 주었다. 제조된 DSSC의 광 변환 효율을 측정하기 위해 Solar simulator 장비를 사용하여 제작된 cells의 효율을 측정하였다.

• Elastomers and Composites
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• 제45권1호
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• pp.51-57
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• 2010

본 연구에서는 친환경적인 특징을 가지면서도 우수한 기계적 특성을 가지고 있어 고분자 복합재료의 보강제로 주목 받고 있는 Cellulose nanowhisker (CNW) 를 염산 혹은 황산을 사용한 산가수분해 방법을 이용하여 Microcrystalline cellulose (MCC) 로 부터 추출하였다. 염산 혹은 황산을 사용하여 추출된 CNW는 직경이 20 에서 30nm 정도였고, 길이가 200 에서 300 nm 로써, 형상학적 측면에서 유사한 특성을 가지는 것을 확인하였다. 또한 전해질 용액의 전기전도도를 이용한 적정 (conductometric titration) 결과 황산을 이용하여 제조되어진 CNW의 경우, 셀룰로오스 표면의 sulfate group 에 의해 나타나는 표면전하 값이 각각 140, 197.78 mmol/kg으로 나타났으며, 염산을 이용하여 제조되어진 CNW 의 경우 셀룰로오스 표면에 약한 전하 값을 가져 표면전하 값을 구할 수 없었다. 황산을 이용하여 추출된 CNW의 열중량 분석 결과 염산을 이용하여 추출된 CNW와 비교하여 열분해 온도가 급격히 감소하는 것을 확인할 수 있었으며, Broido's method를 이용하여 정의 되어진 열분해 거동에 대한 활성화 에너지 역시 상대적으로 낮음을 확인할 수 있었다.

• 아동학회지
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• 제11권2호
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• pp.5-23
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• 1990

The purpose of this study was to investigate the acquisition of number-word systems of young children. Specifically, the acquisition of Korean Number-Words(KNW) was compared with the acquisition of Chinese-derived Number-Words(CNW). The subjects included 120 children aged 2:5 to 5:11. The subjects oral counting using the two number word systems were audiotaped. Two coders transcribed the tapes. The data were analyzed by content analysis with descriptive statistics. The findings of this study showed that the acquisition of KNW began from around age two and the acquisition of CNW from around age three. From then, the acquisition of the two number-word systems was parallel. The acquisition of number-words began from the age of 2 years, increased slowly to the age of 4. and then increased rapidly after the age of 5. Although KNW were acquired earlier than CNW, at around the age of 5 years the acquisition of CNW surpassed the acquisition of KNW. The acquisition of number words consists of four developmental levels: Level I: beginning of acquisition of traditional KNW only Level II: beginning of acquisition of CNW with extension of KNW Level III: parallel extension of the two number-word systems Level IV: superior acquisition of CNW. The major error through all stages in the sequence of number words was the omission of one number-word. Younger children produced errors of omission of one, two or three number-words, whereas older children produced errors of nonstandard number-words and repetition.

• 한국전기전자재료학회논문지
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• 제26권9호
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• pp.686-689
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• 2013

The carbon nanowall (CNW) is a carbon-based nanomaterials and it was constructed with vertical structure graphenes and it has the highest surface density among carbon-based nanostructures. In this study, we have checked the growth properties of CNW according to the substrate angle. Microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow CNW on Si substrate with methane ($CH_4$) and hydrogen ($H_2$) gases. And, we have changed the substrate angle from $0^{\circ}$ to $90^{\circ}$ in steps of $30^{\circ}$. The planar and vertical conditions of the grown CNWs according to the substrate angle were characterized by a field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). In case of the growth angle increases, our experimental results showed that the length of the CNW was shortened and the content of carbon component was decreased.

• 전기학회논문지P
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• 제63권4호
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• pp.351-355
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• 2014

Graphite electrodes are used for secondary batteries, fuel cells, and super capacitors. Research is underway to increased the reaction area of graphite electrodes used carbon nanotube (CNT) and porous carbon. CNT is limited to device utilization in order to used a metal catalyst by lack of surface area to improve. In contrast carbon nanowall (CNW) is chemically very stable. So this paper, microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow carbon nanowall (CNW) on Si substrate with methane ($CH_4$) and hydrogen ($H_2$) gases. To find the growth properties of CNW according to the reaction gas ratio, we have changed the methane to hydrogen gas ratios (4:1, 2:1, 1:2, and 1:4). The vertical and surficial conditions of the grown CNW according to the gas ratios were characterized by a field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy measurements showed structure variations.

• Transactions on Electrical and Electronic Materials
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• 제16권4호
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• pp.198-200
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• 2015

The microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow a carbon nanowall (CNW) on a silicon (Si) substrate with hydrogen (H₂) and methane (CH₄) gases. To find the growth mechanism of CNW, we increased the growth time of CNW from 5 to 30 min. The vertical and surficial conditions of the grown CNWs according to growth time were characterized by field emission scanning electron microscopy (FE-SEM). Energy dispersive spectroscopy (EDS) measurements showed that the CNWs consisted solely of carbon.

• 한국동물학회:학술대회논문집
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• 한국동물학회 1995년도 한국생물과학협회 학술발표대회
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• pp.180.1-180
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• 1995

No Abstract, See Full Text

• International journal of advanced smart convergence
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• 제1권1호
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• pp.48-51
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• 2012

The conventional method for filtering force plate data, low-pass filtering, does not always give accurate results when applied to force data from a custom-made, instrumented treadmill. Therefore, this study compares low-pass filtered data to the same data passed through a wavelet filter. We collected data with the treadmill running. However these include motor noise with ground reaction force at two force plates. We found that he proposed wavelet method eliminated motor noise to result in more accurate force plate data than the conventional low-pass filter, particularly at high speed motor operation. In this study we suggested the convolution wavelet (CNW) which was compared to that of a low-pass filter. The CNW showed better performance as compared to band-pass filtering particularly for low signal-to-noise ratios, and a lower computational load.

• 한국전기전자재료학회논문지
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• 제27권4호
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• pp.217-220
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• 2014

Graphite electrodes are used for secondary batteries, fuel cells, and super capacitors. Research is underway to increase the reaction area of graphite electrodes. In this study, we have investigated the growth properties of carbon nanowall (CNW) according to the ingredient of gas. Microwave plasma enhanced chemical vapor deposition (MPECVD) system was used to grow CNW on Si substrate with a variety of the reaction gas. The planar and vertical growth conditions of the grown CNWs according to the ingredient of the gas were characterized by a field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). The electrical characteristics of CNWs were analyzed using a 4-point probe.