• 아시안잔디학회지
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• 제18권1호
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• pp.29-36
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• 2004

The efficient refinement of seed is required to reduce the cost and labor input in artificial propagation of wild plant. This study was carried out to develop methods for collecting and refining tiny seeds from wild plants. For obtaining Phragmites communis seeds, the inflorescence was cut into small fragments using a Straw Cutter and subsequently detached pappus hairs from seed coat by Hammer Mill. The primary refined seeds were passed 1.0 mm sieve. The screened seeds were subjected to Seed Blower with wind speed of 0.25 mㆍsec-1 to collected intact and well-ripen seeds. The seeds of Imperata cylindrica were refined as follows. Inflorescences were cut using a Straw Cutter first. The pappus was removed from cut fragments using a Hammer Mill and subsequently subjected to Seed Scarifier at 500rpm for 60 sec. for further separation. The separated seeds were passed 1.0 mm screen and collected after blowing with Seed Blower of wind speed of 0.15 mㆍsec-1. When the amount of seed was too little to refine with Seed Scarifier and Blower, the procedure was slightly modified from the procedure described above. The crude seed mixture obtained from Hammer Mill step was hand-refined roughly and then immersed into cone. (95%) sulfuric acid for 2 min. and collected floating portion after dilution of sulfuric acid solution 100 times with tap water. The collected seeds were dried and passed 0.149 mm sieve. During seed refining process using mechanical or sulfuric acid treatments, a small portion of damaged seed were evolved, however, the amount was not noticeable as compared to the total amount of collected seeds. Because the germination percentages between hand-refined seeds and seeds refined by above methods were not statistically different, the developed procedures for refining tiny seed of wild plants are helpful to reduce the cost and labor input in artificial propagation of two species.

• 전산구조공학
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• 제4권4호
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• pp.135-144
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• 1991

본 논문에서는 해양구조물에 작용되는 파력을 산정하고 구조물-유동의 상호작용을 해석하기 위하여 유동장을 유한요소법으로 모형화하여 해석할 때에, 효과적으로 적용될 수 있는 유체의 3차원 무한요소를 개발하였다. 유동의 수식화는 선형파동이론에 근거하였고, 구조물의 크기가 비교적 큰 경우를 대상으로 함으로써 유동의 관성력항이 지배적이므로, 점성저항력의 영향을 무시하였다. 유동의 지배방정식이 속도포텐셜에 대한 라플라스 방정식으로 주어지고, 구조물의 표면, 수면 및 해저면을 경계로 하여, 수평방향으로는 무한대로 펼쳐진 영역에서 정의된 문제를 효과적으로 해석하기 위하여, 두 종류의 유동요소를 개발하였다. 하나는 무한원방향으로 방사되는 파를 모형화 하기 위한 무한 요소이며, 다른 하나는 심해조건에서 유용하게 적용될 수 있는 가상바닥경계요소이다. 본 연구에서 제안한 유동요소들의 유용성과 효율성은 여러가지의 부유식 해양구조물에 대한 예제해석을 통하여 입증하였다. 같은 에제에 대하여 다른 방법으로 해석한 타 문헌상의 결과와 비교할 때, 본 연구에서 개발한 유동요소를 사용한 방법이 매우 좋은 결과를 줌을 알 수 있었다.

• 대한조선학회논문집
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• 제50권4호
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• pp.224-231
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• 2013

The concept of the natural frequency is useful for understanding the characters of oscillating systems. However, when a circular cylinder floating horizontally on the water surface is heaving, due to the hydrodynamic forces, the system is not governed by the equation like that of the harmonic one. In this paper, in order to shed some lights on the more correct use of the concept of the natural frequency, a problem of the heaving circular cylinder is analyzed in the time domain. The equation of motion, an integro-differential equation, was derived following the fashion of Cummins (1962), and its coefficients including the retardation function were obtained using the numerical solution of Lee (2012). The equation was solved numerically, and the experiment was also carried out in the CNU flume. Using our numerical and experimental results, the natural frequency was defined as its average value given by the motion data excluding those of the initial stage. Our results were then compared with those of the existing investigations such as Maskell and Ursell (1970), Ito (1977) and Yeung (1982) as well as the newly obtained results of Lee (2012). Comparison showed that the natural frequency obtained here agrees well with that of Lee (2012), which was found through the frequency domain analysis. It was also shown that the approximation of heaving motion by a damped harmonic oscillation, which was regarded as suitable by most previous investigators, is not physically suitable for the reason that can be clearly shown through comparing the shape of MCFRs(Modulus of Complex Frequency Response). Furthermore, we found that although the previous approximations yield the damping ratio significantly different from our result the magnitude of natural frequency is not much different from our result.

• Journal of Periodontal and Implant Science
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• 제35권2호
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• pp.311-319
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• 2005

In order to examine the effects of advanced periodontitis on the dental pulps, 38 extracted human teeth were examined histologically. The 38 teeth had a positive or negative state in the electric pulp test(EPT). In addition, almost of the 38 teeth had a deep pocket and severe mobility, and floating state. A medical and dental history was elicited. The extracted teeth fixed in 10% neutral formalin solution. The general tissue processing method was followed. The tissue block including the teeth was prepared for optical microscopy using hematoxillin-eosin staining. Among the 38 periodontally involved teeth, the dental pulps were respectively intact in 12(31%), and a pulp stone(or linear calcifications) was found in 18 teeeth(47%). In addition, 17 teeth(44%) had pulps exhibiting inflammatory reactions with varying intensities, such as hyperemia, pulp abscess, pulp necrosis. Among the 38 periodontally involved teeth, 37 teeth tested a positive to the EPT, and 7 teeth tested negative. The EPT positive 37 teeth had various histological features such as 7 normal pulp(18%), 17 pulp stone(44%), 1 hyperemia (2%), 9 pulpitis(23%), 5 root resorption(13%), 3 pulp abscess(7%), and 3 pulp necrosis(7%), In conclusion, it is suggested that in the EPT positive teeth, advanced periodontally involved teeth can cause inflammation of the dental pulp.

• 펄프종이기술
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• 제46권5호
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• pp.79-87
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• 2014

The enrichment with nutrients in rivers and lakes becomes serious problems in Korea. As the environmental friendly solution, the phytoremediation are getting more attention and the water hyacinth could be a strong candidate plant for this. Water hyacinth is a free floating freshwater plant proven to be a effective plant used for a purification of a polluted lakes, sewage wastewater, and livestock wastewater. The biggest obstacles for application of water hyacinth in Korea could be the disposal of the water hyacinth before winter, because there is no feasible use for the water hyacinth until now. In this study, the characteristics of water hyacinth were deeply investigated for providing background data to develop appropriate application of the water hyacinth. The water hyacinth was fractioned three parts, leaf, air blader, root of which morphological properties were evaluated with microscope and field emission scanning electron microscope (FE-SEM). The water contents of each parts of the water hyacinth were 87% for leaf, 96.5% for air bladder, 94.6% for root. The chemical compositions of each parts were also measured and showed around 29% of hot water extract in leaf and air bladder, 42% holocellulose for leaf, 47% holocellulose for air bladder. The application of water hyacinth biomass without root parts to papermaking provided bulkier structure, but the tensile strength was decreased.

• 상하수도학회지
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• 제19권2호
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• pp.149-154
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• 2005

Conventionally used flocculation tanks require large space and high energy requirement for mixing. Static flocculators using gravel bed filter operate at a lower flow rate ($5-10m^3/m^2{\cdot}h$). Further, the cleaning of this system is difficult. A novel high rate static flocculator/filter developed at UTS packed with buoyant media such as polystyrene, polypropylene has been found to operate at higher filtration rates (30-45 $5-10m^3/m^2{\cdot}h$). They can easily be cleaned with minimal energy. Detailed experiments conducted with an artificial kaolin clay solution show that buoyant media is an excellent static flocculator in producing uniform filterable microflocs (12-15 m) even when it is operated at a high rate of 30-40 m/h. Detailed filtration experiments were conducted in a wastewater treatment plant to treat the biologically treated effluent with a floating media of depth of 120 cm. This filter was able to remove majority of phosphorus and remaining solids. It reduced significantly the fecal coliforms and fecal streptoccoci, thus requiring less amount of chlorine for disinfection. The advantage of this system is the low energy and water requirement for cleaning of filter bed. The periodic backwash adopted 30 seconds air and water and 30 seconds water cleaning every 90 minutes filter operation. Thisis equivalent to 1-2% of filtered water production. Mechanical cleaning system on the other hand, requires very low energy requirement (<1% of filtered water production).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.311-311
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• 2009

Carbon nanotubes (CNTs) belong to an ideal material for field emitters because of their superior electrical, mechanical, and chemical properties together with unique geometric features. Several applications of CNTs to field emitters have been demonstrated in electron emission devices such as field emission display (FED), backlight unit (BLU), X-ray source, etc. In this study, we fabricated a CNT cathode by using filtration processes. First, an aqueous CNT solution was prepared by ultrasonically dispersing purified single-walled CNTs (SWCNTs) in deionized water with sodium dodecyl sulfate (SDS). The aqueous CNT solution in a milliliter or even several tens of micro-litters was filtered by an alumina membrane through the vacuum filtration, and an ultra-thin CNT film was formed onto the alumina membrane. Thereafter, the alumina membrane was solvated by acetone, and the floating CNT film was easily transferred to indium-tin-oxide (ITO) glass substrate in an area defined as 1 cm with a film mask. The CNT film was subjected to an activation process with an adhesive roller, erecting the CNTs up to serve as electron emitters. In order to measure their luminance characteristics, an ITO-coated glass substrate having phosphor was employed as an anode plate. Our field emitter array (FEA) was fairly transparent unlike conventional FEAs, which enabled light to emit not only through the anode frontside but also through the cathode backside, where luminace on the cathode backside was higher than that on the anode frontside. Futhermore, we added a reflecting metal layer to cathode or anode side to enhance the luminance of light passing through the other side. In one case, the metal layer was formed onto the bottom face of the cathode substrate and reflected the light back so that light passed only through the anode substrate. In the other case, the reflecting layer coated on the anode substrate made all light go only through the cathode substrate. Among the two cases, the latter showed higher luminance than the former. This study will discuss the morphologies and field emission characteristics of CNT emitters according to the experimental parameters in fabricating the lamps emitting light on the both sides or only on the either side.

• 자원리싸이클링
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• 제27권1호
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• pp.45-54
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• 2018

플라이애시의 부유선별 과정에서 교반속도와 공기주입량과 같은 기계적 요소 변화에 따른 영향을 알아보고자 본 연구를 실시하였다. 본 연구에서는 미연탄소 함량이 약 3.4 ~ 3.7% 수준인 화력발전소 플라이애시를 사용하였다. 대표적인 부유선별의 선별 요소인 pH, 교반속도, 포수제 첨가량, 기포제 첨가량 변화에 따른 영향을 살펴보았을 때, Safflower oil을 포수제로 사용하여 첨가량을 800 g/ton, pH 7, 교반속도 1,200 rpm, 기포제 첨가량이 400 g/ton였을 때, 미연탄소 회수율과 미연탄소 함량이 각각 63%, 34%로 나타났다. 이 때 부상물 SEM/EDS 분석을 통해 알아본 결과, 구형의 플라이애시 미립자가 미연탄소 내에 고용되거나, 광액 내에 가라앉지 못하고 기포와 함께 부유함으로써 미연탄소의 함량을 낮추는 것으로 나타났다. 교반속도와 공기주입량과 같은 기계적 요소를 변화시킨 실험에서는 공기주입량 8L/min, 교반 속도 900 rpm에서 미연탄소 회수율 74%, 미연탄소 함량 67%인 것으로 나타났다. 이는 낮은 교반속도와 추가 공기주입으로 인하여 광액 내 와류의 강도가 낮아져, 미립의 플라이애시 입자가 미연탄소와 함께 부유되는 현상을 방지됨으로써, 미연탄소 회수율과 미연탄소 함량이 향상된 것으로 나타났다. 또한, 교반속도와 공기주입량을 각각 800 rpm, 6 L/min으로 설정하였을 때 미연탄소 회수율과 미연탄소 탄소함량이 각각 80%, 70%로 향상되어 가장 우수한 것으로 나타났다.

• 원예과학기술지
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• 제34권6호
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• pp.878-885
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• 2016

본 연구는 밀폐형 식물생산시스템에서 아이스플랜트의 생육과 기능성물질에 따른 광질의 효과를 구명하고자 수행하였다. 아이스플랜트 종자를 128구 플러그 트레이에 암면을 이용하여 파종하였고, 묘는 밀폐형 식물생산시스템에서 담액식 수경재배를 이용하여 정식하고 재배하였다(EC $1.5dS{\cdot}m^{-1}$, pH 6.5). 정식 후 2주째부터 아이스플랜트의 블러더 세포 발달을 위해 2mM의 염화나트륨(NaCl)을 첨가하여 공급하였다. 실험에 이용된 다른 광질을 가진 세 개의 인공광원으로는 형광등과 RW LED, RBW LED를 사용하였다. 이때 광주기는 14/10(명기/암기), 광도는 $150{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ PPFD로 설정했다. 결과적으로 엽면적, 지상부와 지하부의 생체중과 건물중은 형광등 처리에서 아이스플랜트의 생육 증진에 가장 효과적이었다. SPAD 값은 형광등과 RBW LED 처리에서 각각 29.8과 30.6으로 높은 값을 나타냈다. 염도는 모든 처리구에서 유의적인 차이가 없었다. 엽록소 형광은 형광등 처리에서 유의적으로 가장 높았다. 총페놀함량과 항산화능은 RBW LED 처리에서 높은 값을 나타냈다. 총플라보노이드 함량은 형광등과 RBW LED 처리에서 유의적으로 높았다. 따라서, 본 결과는 형광등 처리에서 아이스 플랜트의 생육이 가장 효과적인 것으로 나타났다. 반면에 기능성물질은R BW LED 처리에서 가장 효과적이었다.

• 생물환경조절학회지
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• 제26권4호
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• pp.386-392
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• 2017

본 연구는 밀폐형 식물생산 시스템에서 다양한 형광등 종류에 따른 시금치 '수시로'의 생육과 기능성물질 함량에 미치는 영향을 구명하기 위해 수행되었다. 종자는 128구 플러그 트레이에 암면을 이용하여 파종되었다. 시금치 묘는 재순환 담액식 수경재배 시스템을 이용하여 EC $1.5dS{\cdot}m^{-1}$, pH 6.5의 밀폐형 식물생산 시스템에 정식되었다. 묘는 3가지 종류의 형광등 #S(NBFHF 32S8EX-D, CH LIGHTING Co. Ltd., China), #O( FHF32SSEX-D, Osram Co. Ltd., Germany), #P(FLR32SS EX-D, Philips Co. Ltd., The Netherlands)에 광도 $150{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ PPFD와 광주기 14/10 (명기/암기)으로 설정했다. 정식 후 재배환경은 온도 $25{\pm}1^{\circ}C$와 상대습도 $60{\pm}10%$ 였다. 정식 후 6주간 각 처리마다 30개체를 재배하였고, 생육 및 기능성 물질 함량을 3주째와 6주째 측정했다. 정식 후 3주째, #O 형광등에서 다른 처리구에 비해 초장과 엽폭이 유의적으로 컸다. 그러나 지하부의 생체중과 건물중은 #P 형광등에서 가장 높았다. 또한 총페놀 함량은 #P 형광등에서 유의적으로 가장 높았다. 정식 후 6주째, #O 형광등에서 초장, 지상부의 생체중 및 건물중에서 시금치의 생육이 향상되는 효과를 보였다. 총페놀 함량도 #O 형광 등에서 다른 처리구에 비해 유의적으로 증가하였다. 그러나 항산화 활성은 모든 처리구에서 유의적인 차이를 나타내지 않았다. 따라서 이러한 결과는 밀폐형 식물생산 시스템에서 #O 형광등 처리가 시금치의 생육과 기능성물질 함량 축적에 효과적인 것으로 나타났다.