• Journal of the Korean Wood Science and Technology
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• 제50권6호
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• pp.392-403
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• 2022

Currently, composite board manufacturing using natural fibers has the potential to expand owing to environmental awareness. To produce a composite board, treatment is required to improve the mechanical and physical properties of the natural fibers. In this study, sodium chloride (NaCl) was used for the chemical treatment. However, studies on chemical treatments using NaCl are limited. This study aimed to investigate the characteristics of kenaf fibers after NaCl treatment. The NaCl treatment concentrations were 1, 3, and 5 wt.% at room temperature, with soaking durations of 1, 2, and 3 h. The tensile strength, strain, and Young's modulus were measured to evaluate the mechanical properties of the fibers. The fiber bundle diameter, weight change owing to treatment, and contact angle were determined to analyze the effect of NaCl treatment. The kenaf fiber bundle treated with 5 wt.% NaCl for 3 h exhibited the highest tensile strength, Young's modulus, reduction in fiber bundle diameter, weight change, and decrease in contact angle compared to those of untreated fiber bundles. The tensile properties of the fiber bundle exhibited a tendency to decrease with increasing fiber bundle diameter. Increasing the soaking duration from 1 to 2 h did not result in a significant decrease in the fiber bundle diameter or an increase in tensile strength. However, a further increase in the soaking duration from 2 to 3 h resulted in a considerable decrease in the fiber bundle diameter and an increase in the tensile strength.

• 대한수학회지
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• 제42권4호
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• pp.621-634
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• 2005

Let$P{\rightarrow}M$ be an oriented $S^2-fiber$ bundle over a closed manifold M and let Q be its associated SO(3)-bundle, then we investigate the ring structure of the cohomology of the total space P by constructing the coupling form TA induced from an SO(3) connection A. We show that the cohomology ring of total space splits into those of the base space and the fiber space if and only if the Pontrjangin class $p_1(Q)\;{\in}\;H^4(M;\mathbb{Z})$ vanishes. We apply this result to the twistor spaces of 4-manifolds.

• 한국의류학회지
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• 제31권11호
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• pp.1565-1573
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• 2007

This research was aimed to investigate the effect of $K_2CO_3$ instead of NaOH on retting of the kenaf bast. We examined the relationship between separation of fiber bundle and tensile strength besides observing the color, handle and cross sectional view for the kenaf fiber retted with various concentration(100, 150, 200, 250, 500, 1000mmol) of $K_2CO_3$ and double retted with 0.5% pectinase after $K_2CO_3$ retting. The one retted on low $K_2CO_3$ concentration, $150{\sim}200mmol$, showed the best result on color, handle and luster. The separation of fiber bundle started even at the low $K_2CO_3$ concentration, 100mmol, and as the $K_2CO_3$ concentration was higher, the size of the fiber bundle was smaller. In the case of 1000mmol, the fiber bundle became irregular, but they were breaking up into certain way. Regardless of $K_2CO_3$ concentration, the thinner the diameters of the kenaf fiber bundle, the stronger tensile strength have appeared. This result corresponds with the result of cross sectional view. Retting on $150{\sim}200mmol\;K_2CO_3$ concentration was most effective on fiber bundle#s separation and tensile strength. The one with double retted with 0.5% pectinase after $K_2CO_3$ retting showed very small size of fiber bundle and low tensile strength compare to the one just retted on $K_2CO_3$. This decrease of tensile strength seem to be related to damage of the fiber resulted by excessive fibrillation.

• Restorative Dentistry and Endodontics
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• 제34권4호
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• pp.364-370
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• 2009

본 연구의 목적은 strain gage와 LVDT (linear variable differential transformer) 변위센서를 이용하여 섬유 보강 복합레진에서 섬유의 방향이 복합레진의 중합수축에 미치는 영향을 알아보기 위함이다. 지름 10 mm, 높이 2 mm의 원반 모양 유동성 복합레진 (Aeliteflo A2, Bisco, Inc., IL, USA) 중앙에 유리섬유 (X-80821P Glass Fiber, Bisco, Inc., IL, USA)를 위치시키고, 섬유가 배열된 장축 방향 (longitudinal)과 수직방향 (transversal)의 중합수축량을 strain gage (Linear S-series 350${\Omega}$, CAS, Seoul, Korea)를 이용하여 각각 측정하였다. 사용된 유동성 복합레진 자체의 free 중합수축을 구하기 위해 지름 7 mm, 높이 1 mm의 원반 모양 시편의 수직 방향 (axial) free 중합수축값을 LVDT로 측정하였다. 중합된 시편들을 절단하여 주사전자현미경으로 복합 레진 내부의 섬유배열을 관찰하고 각 군에서 측정된 평균 수축값들을 ANOVA로 비교하였고 Scheffe post-hoc test로 사후 검정하였다 (${\alpha}$=0.05). 섬유가 배열된 평면 상에서 복합레진의 중합수축 (radial shrinkage)은 섬유와 평행한 방향에서 감소하고 섬유와 수직한 방향에서 증가했다 (p<0.05). 본 연구의 결과 섬유 보강 복합레진으로 스플린트나 수복물을 제작할 때 중합수축량은 보강된 섬유의 배열방향에 따라 큰 차이가 남을 알 수 있었다.

• 멤브레인
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• 제23권4호
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• pp.257-266
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• 2013

본 연구에서는 고온에서 유기용매를 정제할 수 있는 고온, 고압에서 안정한 상업화 규모의 고효율 중공사 투과증발막, 막모듈 개발, 상업 규모의 막분리 장치시스템 개발을 수행하였는데 구성 요소기술은 1) 고온 고압 하에서 사용할 수 있는 브레이드 강화 중공사 막제조, 2) 중공사 막모듈 제조, 3) 막 탈수, 정제장치 시스템 설계 및 제작기술등을 개발하였다. 개발 중 공사 투과증발막은 독일의 슐츠막 보다 막 안정성과 막 성능이 우수하였으며, 막면적 4.6 $m^2$의 고효율 상업적 규모의 중공사막모듈을 개발하였고, 200 L/hr 이상의 처리용량의 Pilot 규모의 투과증발 막장치 시스템을 개발하였다. 기존 평막 혹은 중공사막에서 모듈에서 볼 수 있었던 모듈내부에 공급액의 dead volume형성, 공급액의 채널링 현상들을 제거하기 위해서 본 개발 중공사막과 막모듈의 특징은 고온, 고압의 유기용매를 중공사막 내부로 공급되어 흐르도록 설계되어 있어 막분리 효율이 우수하며 특히 기존의 막제품의 대비 막모듈 가격이 저렴하고, 막성능 및 치수안정성이 우수하다. 또한 공급액의 열손실 적어 에너지 효율이 우수할 뿐 아니라 막모듈 내에 중공사막 사이의 간격이 일정하여 가해주는 진공이 균일하게 각 중공사막의 투과부 표면에 전달될 수 있기 때문에 투과된 투과물을 막 표면으로부터 효과적으로 제거할 수 있으므로 투과속도 또한 우수하다.

• 대한본초학회지
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• 제22권2호
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• pp.109-114
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• 2007

Objectives : A morphological classification among Sinomenium acutum, Cocculus trilobus and Aristolochia fangchi was made through microscopic observation. Method : The slice of the tested material made by paraffin section technique was colored with Safranine Malachite Green contrast methods, and then observed and photographed by olymphus-BHT. Result : 1. Fiber bundles of pericycle in S. acutum are like a crescent moon, stone cells were found among fiber bundles, and starch grain and raphides of calcium oxalate were included in parenchyma. 2. C. trilobus has the fiber bundle of pericycle resembling a crescent moon, but does not have the raphidesof calcium oxalate. 3. A. fangchi has the raphides of calcium oxalate, but does not have the fiber bundles of pericycle. 4. Stems and roots of S. acutum arc mostly similar, but only stems have the pith. Conclusion :' C. trilobus and A. fangchi can be distinguished from each other by the fiber bundles of pericycle and the raphides of calcium oxalate.

• Membrane and Water Treatment
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• 제4권1호
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• pp.53-67
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• 2013

In this study, ageing characteristics of an industrial hollow-fiber membrane module were investigated after 50 months of drinking water production. For this purpose, the industrial module was opened to make 18 smaller modules with hollow-fibers taken from different parts of the industrial module. These modules were probed by the use of a magnetic nanoparticle (NP) challenge test based on magnetic susceptibility (K) measurement of permeate. No magnetic susceptibility was detected in permeate when the challenge test was performed on an intact membrane module, indicating the complete retention of nanoparticles by the membrane. The compromised membrane module can be successfully detected by means of magnetic susceptibility measurement in permeate. So, this study clearly demonstrates that ageing of ultrafiltration membranes can be monitored by measuring the magnetic susceptibility of permeate from an ultrafiltration membrane module. These results showed that the hollow fibers in the center zones of the bundle would age faster than those in the outer zones around the bundle. This result is in agreement with numerical simulation (Daurelle et al. 2011).

• Composites Research
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• 제26권3호
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• pp.160-164
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• 2013

In this study, the effect of phosphoric acid (PA) as a fiber spinning aid on the strength increase of polyacrylonitrile (PAN) nano-fibers by using modified mechano-electrospinning technologies has been analyzed. The medium carbonization temperature of $800^{\circ}C$ has been selected for the future economic production of these new materials. The concentration of PAN in dimethyl sulfoxide (DMSO) was fixed as 5 wt%. The weight fraction of PA was selected as being 2%, 4%, 6%, and 8% in comparison to PAN. These solutions have been used to make the nanofibers. The mechano-electrospinning apparatus installed in KRICT was made by our own design. By using this apparatus the continous and highly aligned precursor nano-fibers have been obtained. The bundle of 50 well aligned nano diameter continuous fibers with the diametr of 10 microns with 6 wt% phosphoric acid for addition showed maximum mechanical properties of 1.6 GPa as tensile strength and 300 GPa as Young's modulus. The weight of final product can be increased 19%, which can improve the economical benefits for the application of these new materials.

• 한국광학회지
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• 제19권2호
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• pp.87-94
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• 2008

공초점 내시 현미경의 경우 살아있는(in vivo) 동물체들의 뇌 속에서의 암세포나 특정 세포를 분석할 수 있으며, 비 침습적으로 얻을 수 있는 기술과 동시에 실시간으로 암을 검출할 수 있는 장점이 있다. 공초점 내시 현미경의 경우 최소 직경과 고 분해능을 요하게 된다. 본 논문은 최소 직경을 가지는 GRIN 렌즈와 유동적으로 움직일 수 있는 광섬유 다발을 연결시킴으로써 보다 측정에 용이하도록 하였다. 직경이 1 mm이고 수치구경이 0.5이며 pitch가 0.25인 GRIN렌즈를 사용하였으며, 광섬유 다발은 30,000개의 코어로 구성된 유동적인 광섬유 다발을 사용하였다. 본 논문은 GRIN 렌즈에 의해서 발생되었던 구면수차는 광학보상자를 이용하여 보정하였다. 그 결과 설계되어진 공초점 내시 현미경 대물렌즈의 경우 종 분해능은 $1.63\;{\mu}m$이고 축상물점과 비축물점에서의 에너지 분포가 100%일 때 각각의 spot size는 축상물점에서 $0.3\;{\mu}m$ 비축물점에서 $0.83\;{\mu}m$의 결과를 얻었으며 보다 값싸고 제작에 용이한 양산 비구면 렌즈로 대체 구현된 결과에서는 종 분해능이 $1.74\;{\mu}m$이고, 축상 물점에 대한 spot size는 $1.1\;{\mu}m$이고 비축물점에서는 spot size가 $2.94\;{\mu}m$로 설계되었다.

• 한국자동차공학회논문집
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• 제12권5호
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• pp.58-65
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• 2004

A cylindrical constant volume combustion chamber was used to investigate the combustion characteristics of stratified methane-air mixture under several initial charge conditions in the author's previous reports. The results showed that the improvement of thermal efficiency and reduction of heat loss was realized simultaneously by using 2-stage injection method. This paper deals with the reason why the stratified combustion has showed better combustion rate through the measurement and analysis of chemiluminescence of C $H^{*}$ and $C_{2}$$^{*}$ radicals. An optic fiber bundle is used to measure the local emission of C $H^{*}$ and $C_{2}$$^{*}$ radicals to map the relationship between the excess air ratio and local radical intensity ratio in the combustion vessel at 5 mm apart form the geometric center. The results show that there exist a relationship between the intensity ratio and the air-fuel ratio. It is revealed that the improvement of combustion rate in a lean-stratified mixture is realized through the 2-stage injection method. method.