• 대한기계학회논문집B
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• 제33권5호
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• pp.381-388
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• 2009

In some portions of nuclear piping systems, stratification phenomena may occur due to the density difference between hot and cold stream. When the temperature difference is large, the stratified flow under diverse operating conditions can produce high thermal stress, which leads to unanticipated piping integrity issues. The objectives of this research are to examine controvertible numerical factors such as model size, grid resolution, turbulent parameters, governing equation, inflow direction and pipe wall. Parametric three-dimensional computational fluid dynamics analyses were carried out to quantify effects of these parameters on the accuracy of temperature profiles in a typical nuclear piping with complex geometries. Then, as a key finding, it was recommended to use optimized mesh of real piping with the conjugated heat transfer condition for accurate thermal stratification analyses.

• 한국작물학회:학술대회논문집
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• 한국작물학회 1997년도 춘계 학술대회지
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• pp.84-85
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• 1997

• 한국약용작물학회지
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• 제11권3호
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• pp.207-211
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• 2003

가시오갈피의 종자번식에서 가장 큰 문제점 중의 하나인 종자의 불량과 발아가 동시에 이루어지지 않는 문제를 해결하고 최대한 많은 묘목을 얻기 위해서는 파종시기의 선택이 중요하다. 파종 전 종자처리를 통하여 성숙정도가 다른 가시오갈피의 파종 후 유묘출현율과 최종생존율을 높이기 위한 기초자료를 얻기 위해 본 연구를 실시한 결과를 요약하면 다음과 같다. 1. $15^{\circ}C$에서 145일 충적 저장한 가시오갈피 성숙종자의 개갑율은 16.6%로 매우 저조하였다. 2. 개갑종자의 기내발아실험에서 $GA_{3}$처리는 최고로 26.6%의 발아율을 보였으나 발아는 동시기에 이루어지지 않았다. 3. 후숙처리후 10일간 저온 처리한 개갑종자에서 파종 전 $GA_{3}$처리는 유묘출현율을 높이는 효과가 있었으나 저온처리는 대체하지 못하였다. 4. 휴면타파를 위한 저온 충적저장전의 종자의 $GA_{3}$처리는 파종 시 개갑종자의 유묘출현율에 영향을 주지 못하였다. 5. 저온저장 40일 경과한 후 파종 전 $GA_{3}$처리는 비개갑종자에서는 유묘출현율과 생존율을 높였다. 개갑종자에서는 유묘출현율은 14.6% 증가하였지만 최종생존율은 오히려 9.4% 감소하였다.

• 한국자원식물학회지
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• 제31권4호
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• pp.363-371
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• 2018

헐떡이풀은 우리나라에서 울릉도에서만 분포하는 자생식물로 전통적으로 약용으로 쓰여왔으며, 관상식물로의 활용도 기대되는 자원식물이다. 본 연구는 헐떡이풀 종자의 휴면타파와 발아를 위한 조건을 확립하고 종자휴면 유형을 분류하고자 수행되었다. 실험은 헐떡이풀 종자에 저온층적처리($5^{\circ}C$에서 0, 12주)와 고온층적처리($23^{\circ}C$에서 0, 4, 8, 12주 처리 후에 $5^{\circ}C$에서 8주, 다시 $23^{\circ}C$에서 배양함), $GA_3$ (0, 10, 100, 1000 mg/L)처리를 수행하였다. 이렇게 처리한 종자는 무균배지에 소독하여 파종하고 온도 $23^{\circ}C$, 광도 $40{\mu}mo{\ell}{\cdot}m^{-2}{\cdot}s^{-1}$ PPFD, 일장16시간 조건의 배양실에서 배양하였다. 헐떡이풀 종자는 자연상태에서 미숙배인 상태로 탈리되며, 종자 내부로의 수분흡수에 대한 물리적인 장벽은 없었다. 그러나 아무 처리 없이 파종하였을 때 30일이 지나도록 전혀 발아하지 않았다. 따라서 헐떡이풀 종자는 형태적 휴면(MD)과 생리적 휴면(PD)을 가지고 있는 것으로 판단하였다. 저온층적처리(0, 12주) 실험의 최종 발아율은 각각 66.7%, 45.6%로 나타났다. 저온처리는 오히려 발아를 약 3주 정도 지연시켰다. 고온층적처리(0, 4, 8, 12주) 실험에서는 최종 발아율이 각각 13.3%, 24.4%, 20.0%, 51.1%로 나타났다. 헐떡이풀 종자의 배는 상대적 고온에서 발달하였다. $GA_3$ 처리는 종자의 휴면을 극복하고 발아를 촉진하였다. $GA_3$ 처리에서의 최종 발아율은 0, 10, 100, 1000 mg/L 처리구에 대하여 각각 33.3%, 45.0%, 42.5%, 72.5%로 나타났다. 위의 결과를 종합하여 헐떡이풀 종자는 non-deep simple 형태생리적 휴면(MPD)을 가지고 있으며, $GA_3$ 처리를 통해 고온을 대체하고 종자의 휴면을 타파할 수 있었다. 이는 한국에 자생하는 헐떡이풀속의 종자휴면에 대해 처음으로 보고한 논문이다.

• 태양에너지
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• 제8권2호
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• pp.46-56
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• 1988

This investigation concerns thermal stratification of the water due to the temperature difference (${\Delta}T=T_{\infty}-T_i$) between the mean temperature of the water in the test tank (1m wide, 1m high, 2.1m long) and the temperature of the inflow water into the tank; flow rate of circulating water and height of the sink diffuser in the test tank. The additional objectives was to observe a stratification phenomena near an interface by measuring the velosities and the temperature difference and investigate an availabilities of the better effective hot water through establishing thermocline near an interface around the bottom of the tank. Following results were obtained through the experiments. 1. When the flow rate was constant and the temperature difference (${\Delta}T=T_{\infty}-T_i$) between the mean temperature of the flow in the test tank and the temperature of the inflow water increased by 5.6, 9.5, 13.5($^{\circ}C$), obtained the better effective advantage of hot water and the stress near an interface increased gradually. 2. When the ${\Delta}T=T_{\infty}-T_i$ was constant and flow rate increased by 4.0, 4.8, 6.4, 8.0 (LPM), obtained the better effective advent age of hot water and the mean stress near an interface increased gradually. 3. When the height of the sink diffuser was 25cm from tank bottom in comparison with 50cm, obtained the better effective advantage of hot water and the mean stress near an interface increased.

• 한국자원식물학회지
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• 제36권6호
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• pp.580-587
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• 2023

Androsace septentrionalis is a grass species restricted to North Korea; however, it is at the brink of extinction due to habitat loss and environmental changes caused by natural disasters and anthropogenic activities. This study was conducted to characterize the dormancy conditions of A. septentrionalis in an effort to conserve this North Korean plant resource. For this purpose, the morphological characteristics and vigor of A. septentrionalis seeds were examined, and its germination characteristics under different temperature conditions (15/6℃ and 25/15℃ ), low-temperature stratification, and gibberellin (GA₃) treatment were determined. The results revealed that A. septentrionalis exhibits non-deep type morpho-physiological dormancy, and low-temperature stratification treatment was not effective in breaking the dormancy of A. septentrionalis seeds. Meanwhile, GA₃ treatment significantly increased the mean germination time, rate, and speed of the seeds. The optimal conditions for the germination of A. septentrionalis seeds were 25/15℃ fluctuating temperature and 500 mg·L¹ GA₃ treatment. The results of this study are useful for the mass propagation of A. septentrionalis.

• 한국해양학회지
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• 제9권1_2호
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• pp.10-18
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• 1974

The cold water mass around the southeast coast of the Korean Peninsula is analyzed by using CSK data from 1966 through 1970. It is shown that this water mass flows down from the region offshore of Jukbyun to the area of Youngil Bay along the 100meter contour line of bottom topography. In ordinary summer conditions when the current velocity in the Korea Strait is usually above about 50cm/sec and the wind direction is southwest, the cold water ascends to the surface and makes the surface temperature gradient large, unless disturbed by a tropical cyclon. The bottom water of the Korea Strait is formed by the stratification after the Tsushima intermediate water and the Japan Sea intermediate water have been mixed. In winter the Tsushima intermediate water with high salinity sinks rapidly around the inlet of the Japan Sea and prevents the Japan Sea intemediate water from entering the Korea Strait.

• 설비공학논문집
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• 제26권7호
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• pp.322-328
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• 2014

Return piping is used in a solar combi-system for heating and hot water supply. When the temperature of the lower side of a storage tank is low due to hot water usage, the returned hot water after heating is mixed with the lower side cold water of the tank, and the useful energy is reduced. We studied the degree of thermal stratification in the tank, using either a diffuser or a manifold to prevent mixing. Using the diffuser, mixing starts from the bottom of the storage tank. On the other hand, the manifold has the marked effect of preventing mixing. As a result of experiments with changing the diameter and number of holes in the manifold, the optimum condition is 8.5 mm diameter and 96 holes, under the condition of 0.3 lpm.

• 대한조선학회논문집
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• 제42권3호
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• pp.183-189
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• 2005

A modeling of a hydraulic-gun-aerator is proposed to set up a design procedure for such devices. The aerators are used to destroy any thermal stratification that are responsible for the degradation of water qualify of lakes. The aerator produces ascending flow by using air bubbies released instantly near the bottom of the lake into a cylindrical pipe installed vertically. Differently form the diffuser-aerators, they can pull up the cold, oxygen depleted water directly to the region of the free surface, and they are believed to work effectively especially for relatively deeper lakes. Their design procedure has not been established yet though, and we propose a model focusing on the exit flow velocity at the top of the aerator through the examination of presently operating devices.

• 아시안잔디학회지
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• 제9권1호
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• pp.1-10
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• 1995

This study was carried out to investigate the method of propagation of Lindera erythrocarpa Makino. The results were as follows: 1. After the treatment of warm stratification for 1 month followed by cold stratification for 3 months, the germination ratio of seeds of Lindera erythrocarpa was from 84.6 to 93.6 percent. But, dry stored seeds lose their viability Quickly and should be placed in pretreatment im-mediately. Also, the seeds of control district germinated from 68.6 to 74.6 percent. So it was confirmed that the seed of Lindera erythocaeicarpa was not doubly dormant. 2. Softwood cuttings of Lindera erythrocarpa with 5,000 ppm IBA on August 4. 1992 resulted in the best rooting of 95.0 percentage. 3.Twenty percent of the graft union were obtained in the green wood grafting in Lindera erythrocarpa on June 7, 1993. And five percent of the graft union were obtained in the hard wood grafting in Lindera erythrcoar pa on April 6. 1993.