• 한국약용작물학회지
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• 제2권1호
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• pp.32-37
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• 1994

본 연구는 시호 종자를 파종했을 때 발아율이 낮고 발아 소요기간이 길어 입모확보가 문제점으로 대두되어 발아율을 향상시키고 단기(短期) 동시 발아시킬 방안을 모색하고자 시호 종자의 발아특성에 대하여 시험한 결과를 요약하면 다음과 같다. 1. 시호종자의 크기는 입경 $2.0{\sim}3.0mm$ 범위이었으며, 평균입경은 삼도시호가 3.0mm 재래시호가 3.1mm이었다. 대립종자일수록 발아기간이 짧고 발아율이 높았다. 2. 시호 종자의 선종에 알맞는 비중은 1.05로 판단되었으며 비중선에 의해 70% 이상의 발아율을 기대할 수 있었다. 3. 시호 종자의 등숙기간은 최소 60일 이상되어야 하며 80일간의 저온 층적 처리에 의해 발아율은20% 이상 증가하였다.

• 한국약용작물학회지
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• 제1권2호
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• pp.104-108
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• 1993

1989년(年)에 건국대학교(建國大學校) 실습농장(實習農場)에서 재배(栽培)하여 채종(採種)한 참당귀(當歸) 종자(種子)를 재료(材料)로 하여 층적(層積), 침종(浸種) 및 Gibberellin처리(處理)한 후(後) 발아상(發牙床)에 넣어 발아율(發芽率), 발아세(發芽勢) 및 발아계수(發芽係數)를 조사(調査)하여 발아율제고(發芽率提高)를 위한 기초자료(基礎資料)로 활용(活用)하고자 수행(遂行)한 시험결과(試驗結果)를 요약(要約)하면 다음과 같다. 1. 층적처리(層積處理)에 의한 발아율(發芽率)은 무처리(無處理)보다 약(約) 30% 증가(增加)를 보였으며, 저온처리(低溫處理)의 효과(效果)는 인정(認定)되지 않았다. 2. 침종처리(浸種處理)에 의한 발아율(發芽率)은 $20^{\circ}C$, 4일(日) 침종구(浸種區)와 $10^{\circ}C$, 6일(日) 침종구(浸種區)에서 가장 높았으며 환수처리(換水處理)는 무처리(無處理)보다 발아억제물질(發牙抑制物質)의 추출효과(抽出效果)가 컸다. 3. Gibberellin처리(處理)에 의한 발아율(發芽率)은 무처리(無處理)보다 약(約) 20% 증가(增加)를 나타내었으며, 침종구(浸種區)에서 2ppm, 무침종구(無浸種區)에서 5ppm에서 발아율(發芽率)이 가장 높았다.

• 한국해안·해양공학회논문집
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• 제27권6호
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• pp.419-423
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• 2015

인공용승구조물은 흐름이 구조물에 의해 상승류와 배후면의 와류가 발생한다. 이때 저층수에 포함된 영양염이 표층으로 이동되고, 표층에선 플랑크톤 및 어류의 생태활동을 촉진시켜, 어업생산성을 향상시키는 역할을 한다. 본 연구에서는 CFD를 이용하여 성층 상태를 고려한 인공용승류의 변화에 대하여 연구하고자 하였으며, 그 결과, 용승효과는 인공용승구조물의 최상부에서 가까울수록 좋은 효과가 나타났으며, 성층상태를 고려하지 않은 경우, 저층에서 표층으로 향하는 상승류 특성만 나타났으나, 성층상태를 고려한 경우, 상승류와 하강류가 반복되는 흐름특성을 확인 할 수 있었다.

• 한국약용작물학회지
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• 제25권4호
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• pp.209-216
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• 2017

Background: Dehisced ginseng seeds need to be stored at cold temperatures for around 3 months to break their physiological dormancy, and thus, to aid in gemination. In the presence of high moisture in such an environment, seed spoilage and pre-germination may lower seed quality and productivity. To improve seed quality during cold-stratification, the effects of seed dehydration and temperature were tested. Methods and Results: In early December, dehisced ginseng seeds were dehydrated at 4 different levels and stored at $2^{\circ}C$ $-2^{\circ}C$, and $-20^{\circ}C$ for 3 months. Germination was carried out on the filter papers moistened with distilled water; emergence of root, shoot, and seed spoilage were assessed. Seed viability was examined by the tetrazolium test. More than 90% of the seeds stored at $2^{\circ}C$ and $-2^{\circ}C$ without drying or endocarp dehydration germinated, but seeds that were dehydrated to have a moisture content (MC) below 31% showed poor germination and lost their viability. In addition, the seeds stored at $-20^{\circ}C$ failed to show effective germination. Conclusions: Seed storage after endocarp dehydration might help to improve seed quality and increase seedling's ability to stand during the spring-sowing of ginseng.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.156-165
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• 2014

This paper is the first investigation on the effect of flow control methods on the part load performance in a spark ignition engine. For comparison of the methods, two control devices, port throttling and masking, were applied to a conventional engine without any design change of the intake port. Steady flow evaluation shows that steady flow rates per unit opening area and swirl ratio are very low compared with the port throttling and saturated from mid-stage valve lift, however, swirl increases slightly as the lift is higher in case of 1/4 masking control. In the part load performance, the effect of simple port throttling on lean misfire limit expansion is limited and insufficient; on the other hand a masking improves the limit considerably without any port modification for increasing swirl. Also the results show that the intake flow control improves the combustion with following two mechanisms: stratification induced by the combination of the flow pattern and the fuel injection timing attribute to ignition ability and the intensified flow ensure fast burn. In addition fuel consumption reduces under the flow controls and the reduction rate is different according to the operation conditions and control methods. At the Stoichiometric and/or low speed and low load the throttling method is more advantageous; however vice versa at lean and high load condition. Finally, the throttling is more efficient for HC reduction than masking, on the other side the NOx emissions increase under the masking and decrease under the port throttling compared with conventional port scheme.

• 대한기계학회논문집B
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• 제34권12호
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• pp.1043-1050
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• 2010

HCCI엔진에는 농도성층화와 열적성층화가 존재하고, 이것들은 착화와 연소과정에 영향을 미치고 있다. 본 연구에서는 예혼합기의 불균질성이 HCCI연소과정에 미치는 영향에 대해서 조사하였다. 우선 4행정광학엔진을 이용하여 잔류가스가 있는 경우와 급속압축장치를 이용하여 잔류가스가 없는 경우의 예혼합기의 불균질성에 대하여 비교분석하였다. DME를 연료로 이용하고 프래밍카메라를 사용하여 2차원화학발광이미지를 취득하였다. 그 결과, 잔류가스가 있는 불균질 한 경우에 4행정엔진실험에서는 연소현상이 공간적으로 연소현상의 시간차이가 발생하였다. 잔류가스가 없는 급속압축장치의 실험에서는 4행정기관의 결과에 비해서 더 적은 공간적인 변화가 존재하는 것을 알 수 있었다.

• 한국자원식물학회지
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• 제27권3호
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• pp.263-270
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• 2014

Loranthus tanakae (Franch. & Sav.) is an endangered species of mistletoe, distributed in Korean peninsula. The objective of our research is to determine the effect of storage duration and conditions [air flow (AF) and air tight (AT)] at different temperatures for survivability and germination of mistletoe seeds, and also to monitor the effect of seed scarification on germination in vitro. The result revealed that the seeds stored in natural conditions (no stratification) showed highest survival rate of 100% and retained up to 93.3% even after two months of storage in natural conditions and showed higher germination percentage (90%) compare to after ripened seeds. However, the seed stored at $0^{\circ}C$ decreased the germination percentage (ranged from 63 to 73%). Therefore, it can be confirmed that mistletoe does not need after ripened treatment to promote germination. Our research also showed that the storage of L. tanaka seeds in freezing temperatures of $-20^{\circ}C$ and in room temperature for long time either in AT or AF conditions caused the loss of survival and germination rate. On the other hand, the chemical scarification (0.01N HCl incubation for 12 hrs. at $38^{\circ}C$) method was proven more effective to enhance germination percentage of L. tanakae. Regarding the temperature regime, $22^{\circ}C$ showed early germination of mistletoe seeds in vitro.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1514-1524
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• 2019

Hydrogen-steam gas mixture may be injected into containment with flow regime varying both spatially and transiently due to wall effect and pressure difference between primary loop and containment in severe accidents induced by loss of coolant accident. Preliminary CFD analysis is conducted to gain information about the helium flow regime transition process from jet to buoyancy plume for forthcoming experimental study. Physical models of impinging jet and wall condensation are validated using separated effect experimental data, firstly. Then helium transportation is analyzed with the effect of jet momentum, buoyancy and wall cooling discussed. Result shows that helium distribution is totally dominated by impinging jet in the beginning, high concentration appears near gas source and wall where jet momentum is strong. With the jet weakening, stable light gas layer without recirculating eddy is established by buoyancy. Transient reversed helium distribution appears due to natural convection resulted from wall cooling, which delays the stratification. It is necessary to concern about hydrogen accumulation in lower space under the containment external cooling strategy. From the perspective of experiment design, measurement point should be set at the height of connecting pipe and near the wall for stratification stability criterion and impinging jet modelling validation.

• 항공우주시스템공학회지
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• 제16권4호
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• pp.35-44
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• 2022

이·착륙하는 항공기에서 발생하는 후류의 거동에 대한 연구는 근접 후행 항공기의 비행안정성과 공항의 경제성 등과 관련하여 매우 중요하다. 특히 이착륙 비행단계에서 발생한 와들의 거동 연구는 지면효과가 반드시 고려해야 한다. 본 연구에서는 기존의 2차원 스펙트럴법에 와도경계조건 및 이미지법을 적용하여, 지면효과가 고려될 수 있는 수치해법을 도출하였다. 개선된 수치기법을 사용하여 얻은 결과를 참고문헌의 수치해석 결과 및 실험결과와 비교하여 타당성을 검증하였다. 특히, 본 연구의 수치해석방법으로 지면근처에서 발생하는 이차와(secondary vortex)의 생성과 박리, 그리고 거동을 예측할 수 있음을 보였다. 향후 본 연구방법을 확장하여 Stratification, Wind Shear 등 다양한 기상조건이 와의 거동에 미치는 영향을 연구할 계획이다.

• 대한기계학회논문집
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• 제18권5호
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• pp.1322-1329
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• 1994

The effect of thermal stratification on the stratified flow past a circular cylinder was examined in a wind tunnel. Turbulent intensities, the rms values of temperature and turbulent convective heat flux as well as the velocity and temperature profiles in the cylinder wake with a strong thermal gradient of $200^{\circ}C/m$ were measured by using a hot-wire and cold-wire combination probe. It is found that the temperature field affects as an active contaminant, so that the vertical growth of vortical structure is suppressed and the strouhal number decreases with increasing the extent of stratification. And also, the wake structure can not sustain their symmetricity about the wake centerline and vertical turbulent motion dissipates faster than that of the neutral case when such a strong thermal gradient is superimposed. It is evident that the turbulent mixing in the upper half section is stronger than that of the lower of the wake in a stably stratified flow because the turbulent intensities and convective heat flux in the upper half section are larger than those of the lower half of the wake.