• 한국환경과학회지
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• 제28권11호
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• pp.1019-1025
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• 2019

The aim of this study was to analyze the light traits in a solar light-collector device and its effects on lettuce growth at an early growth stage. The three hyper parameters used were the reflector diameter (2 cm and 4 cm), coating inside the reflector (chrome-coated, non-coated) and distance from the light fiber (15 cm and 20 cm). The results showed that light efficiency, which is the ratio of light intensity inside the fiber to the solar intensity, improved by 41.1 % when using a 2 cm diameter chrome-coated reflector at a distance of 15 cm from the light fiber; whereas it only improved by 20.6% when a non-coated reflector was used. As the reflector size was increased to 4 cm, the light efficiency for the coated and non-coated reflectors increased by 28.5 % and 26.4 %, respectively, hence, no significant difference was observed. When the light fiber was placed at a distance of 20 cm, the increase in light efficiency with coating treatment was 8 % higher than without coating treatment. We also compared the efficiency of light-fiber treatment with that of LED treatment in our lettuce nursery, and observed that the plants exhibited better growth with light-fiber treatment. We observed an average increase of 1.7 cm in leaf height, $7cm^2/plant$ increase in leaf area, and 32 mm increase in root length upon light-fiber treatment as opposed to those observed with LED treatment. These findings indicate that the collector light-fiber is economically feasible and it improves lettuce growth compared with the LED treatment.

• 한국지반공학회논문집
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• 제16권6호
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• pp.87-95
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• 2000

A series of consolidated undrained triaxial compression testes were performed to increase field applications of soil admixtures mixed with short fiber. Kaolin clay and three types of fiber were selected and auto cutter was used to obtain reliable length of fibers. Remolded soil specimens were tested for obtaining the basic data to be applied to the reinforcement of soft clay, embankment or barrier and clay liner of wastes landfill etc. Conversion equations from weight to volume of clay mixed with short fiber are introduced and relationships between fiber content and fiber concentration are derived. It is found that reinforcing effect by aspect ratio and mixing ratio of short fiber decreases as confining pressure increases. The best efficient reinforcing effect is given at the aspect ratio of 80~120 and the fiber content of 1.2%~2.4% and the fiber diameter of 0.27mm.

• 한국세라믹학회지
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• 제56권6호
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• pp.577-582
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• 2019

Recently, E-glass fiber is the one of most widely used ceramic fiber for aerospace fields. Recycling technology for waste of wind power blades is arising issue for reasons of low manageability and high cost of wastes. Though glass fiber is perfectly dissolved in hydrofluoric acid, low cost for recycling and harmless to human is important for recycling of blades. Chemically melted glass fiber will be used as different purpose like accelerator of hardening for shotcrete. In this study, dissolution process of glass fiber is tested in NaOH solution at low temperatures. In addition, difference in diameter reduction of glass fiber is observed by various alkali concentration and reaction times, treatment temperatures using FE-SEM.

• Structural Engineering and Mechanics
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• 제66권4호
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• pp.477-485
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• 2018

This study aims to investigate the influence of individual and hybrid fiber on the local bond-slip behavior of medium and high strength concrete after exposure to different high temperatures. Tests were conducted on local pullout specimens (150 mm cubes) with a reinforcing bar embedded in the center section. The embedment lengths in the pullout specimens were three times the bar diameter. The parameters investigated include concrete type (control group: ordinary concrete; experimental group: fiber concrete), concrete strength, fiber type and targeted temperature. The test results showed that the ultimate bond stress in the local bond stress versus slip curve of the high strength fiber reinforced concrete was higher than that of the medium strength fiber reinforced concrete. In addition, the use of hybrid combinations of steel fiber and polypropylene fiber can enhance the residual bond strength ratio of high strength concrete.

• Fibers and Polymers
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• 제5권3호
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• pp.171-176
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• 2004

Fiber fineness characteristics are important for yarn production and quality. In this paper, degummed bast fibers such as hemp, flax and ramie have been examined with the Optical Fiber Diameter Analyzer (OFDA100 and OFDA2000) systems for fiber fineness, in comparison with the conventional image analysis and the Wira airflow tester. The correlation between the results from these measurements was analysed. The results indicate that there is a significant linear co-relation between the fiber fineness measurement results obtained from those different systems. In addition, the mean fiber width and its coefficient of variation obtained from the OFDA100 system are smaller than those obtained from the OFDA2000 system, due to the difference in sample preparation methods. The OFDA2000 system can also measure the fiber fineness profile along the bast fiber plants, which can be useful for plant breeding.

• 한국해양공학회지
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• 제16권4호
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• pp.48-53
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• 2002

Fiber-reinforced composites are extensively used in electronic, ship and aerospace applications due to their high strength and high toughess. In these applications, they are often subjected to localized heat damage due to various sources. In order to ensure their reliability, it is important to predict their residual properties using nondestructive evaluation thchniques. Fabric fiber composite specimens were manufactured with six layers of the glass-fiber prepreg and the carbon-fiber prepreg, respectively. The specimens were subjected to a localized heat damage using a heated copper tip with a diameter of 10mm at 35$0^{\circ}C$(CFRP) and 30$0^{\circ}C$(GFRP), respectively. The specimens were then subjected to tension tests while acoustic emission (AE) activities of specimens were collected. The AE activity of all specimens showed three types of distinct frequency regions. Those are matrix cracking, failure of the fiber/matrix interface and fiber breakage.

• Fibers and Polymers
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• 제2권4호
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• pp.178-183
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• 2001

A pitch precursor for a general purpose carbon fiber was prepared by condensation of pyrolized fuel oil (petroleum residual oil) with bromine under nitrogen blowing. such a condensation raised the softening point of the pitch from 4$0^{\circ}C$ to $265^{\circ}$ with a yield of 43%. The pitch precurosr showed an enhanced aromaticity and enlarged molecular size, which led to a reduction in molecular mobility and optical isotropy. The precursor was spun into fibers of $20\mu\textrm{m}$ diameter at a take-up speed of 700m/min. The fiber was stepwise stabilized in air and carbonized in Ar gas to obtain an isotropic carbon fiber. The carbon fiber exhibited tensile strengths of 500-800 ㎫though the fiber was formed via a crude method. The electric conductivity of the carbon fiber was relatively high, 2.2$\times$$10^2$S/cm, sufficient to be used as electrode materials.

• Food Science and Biotechnology
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• 제17권5호
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• pp.959-964
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• 2008

This study evaluated the effects of dietary fiber extracted from rice bran (rice bran fiber) on the quality of low-fat tteokgalbi. The controls were formulated with 20% added fat. Test samples of tteokgalbi were produced with 5 different formulations containing 1, 2, 3, 4, and 5% rice bran fiber as a fat replacer, in addition to 10% fat. The control had the highest fat content, energy value, cooking loss, reduction in diameter, reduction in thickness, CIE $L^*$-value (lighness), and color of sensory properties. The tteokgalbi containing rice bran fiber had higher moisture, protein, ash, and carbohydrate contents than the controls. Tteokgalbi with 3% rice bran fiber had the lowest cooking loss, reduction in diameter, and reduction in thickness. Meat products containing 2 and 3% rice bran fiber had a higher overall acceptability similar to the high fat control.

• Composites Research
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• 제16권2호
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• pp.26-32
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• 2003

레이저 융착된 광섬유의 절단 부위에 대한 보호를 위한 관심이 크게 높아지고 있다 일반적으로 절단된 광섬유의 융착부분은 다른 부위에 비해 상대적으로 매우 취약하며 이러한 이유로 광섬유를 광 통신망에 사용할 때 동일 부분에서의 손실이 추가적으로 일어날 수 있다 일반적으로 광섬유 융착 부위는 일반 광섬유의 파괴 강도에 비해 약 1/10인 0.4～l kg로 감소된다. 이러한 이유로 인해 광 융착 부위의 보강이 절실히 요구되고 있다. 그러나, 이러한 구조물의 대부분이 철심 형태의 구조물을 삽입한 슬리브로 보강됨에 따라 굽힘에 대해 효과적으로 대응하지 못할 뿐 아니라 일단 구조물이 굽혀졌을 경우에는 지속적인 광 손실을 발생시키는 요인이 된다. 이러한 문제점을 보완하기 위하여 복합재료로 제작된 코일형 스프링 구조물 형태의 슬리브가 제안되었다. 이러한 슬리브는 기존의 슬리브의 취약점이었던 직하중에 대해 서로 효과적으로 반응할 뿐 아니라 굽힘 및 인장/압축 하중에도 효과가 있음을 알 수 있었다.

• 한국음향학회지
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• 제19권2호
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• pp.3-7
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• 2000

본 논문은 air cavity가 삽입된 중공 층상복합체 맨드릴형 광-음향센서의 감도특성에 관한 것이다. 유한요소법으로 air cavity의 두께, 포밍(foaming)층의 두께 및 맨드릴의 내경/외경비 등의 형상변수에 따른 광-음향센서의 감도특성을 분석하였다. 그 결과, 두꺼운 air cavity 및 얇은 포밍층이 설치되고, 상대적으로 높은 내경/외경 비를 갖는 맨드릴을 사용하는 것이 음향감도의 향상을 위하여 바람직하다. Air cavity를 삽입한 중공 층상복합체 맨드릴을 사용할 경우, 음향감도는 air cavity가 없는 중공 층상복합체 맨드릴형 센서에 비해 약 0.8dB 정도 향상되는 것으로 나타났다.