• Journal of Practical Agriculture & Fisheries Research
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• v.25 no.1
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• pp.14-19
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• 2023

In summer, the natural ventilation performance for varying greenhouse width is very important in the glasshouses for year round cultivation. The effect of the side openings and greenhouse width on natural ventilation performance was analyzed by simulation. The necessary ventilation rate with different solar radiation transmittance increased significantly when the outside temperature grows higher. The necessary ventilation rate of 40% transmittance was about half of that of 90% transmittance. In consequence, shading effect on temperature control in greenhouse is significant in summer. When the total area of the openings for ventilation is constant, the maximum ventilation rate happens when the area of roof openings is equal to the area of side openings. This maximum ventilation rate is about 3 times of that of the greenhouse with roof openings and without side openings. Therefore, the side openings are advantageous to improve the natural ventilation in greenhouses. As the greenhouse width increases, the influence of side openings on the ventilation rate is becoming smaller. If the natural ventilation rate of the greenhouse with roof and side openings is to become double of that of the roof openings only, the width should be narrower than 38.4m for the Venlo type and 64m for Wide span type.

• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.93-100
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• 2006

The lateral soil movement in soft grounds undergoing improvement with application of vertical drains is analyzed on the basis of monitoring data at three fields, in which fifty six monitoring sites are located. Based on the investigations, the criterions are suggested to predict the lateral soil movement. In order to predict the lateral soil movement in the improved soft grounds by using the dimensionless parameter R suggested by Marche & Chapuis (1974), it is desirable that the maximum lateral displacement in the soft ground below the toe of embankment should be applied to calculate R instead of the lateral displacement at the toe of embankment. The lateral soil movement may increase rapidly, if the safety factor of slope is less than 1.4 in case of high ratio of H/B (Thickness of soft ground/Embankment width) such as 1.15 or is less than 1.2 in case of low ratio of H/B such as 0.05. Also, the graph suggested by Tschebotarioff (1973), which illustrates the relationship between the maximum height of embankments and the undrained shear strength of soft grounds, can be applied to the evaluation for the possibility of the lateral soil movement due to embankments on soft grounds.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.47-47
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• 2022

단자엽식물은 잎의 곡선과 직선의 조화가 아름다워 관상용으로 가치가 높은 식물이다. 이로 인해 자생 단자엽식물의 실내 관상 및 조경용 소재개발 연구가 활성화되고 있으나 재배에 대한 정보는 미비한 실정이다. 본 연구에서는 국내 자생 단자엽식물인 참김의털[Festuca ovina L. var. coreana (St.-Yves) St.-Yves], 청사초(Carex breviculmis R.Br.), 골풀[Juncus decipiens (Buchenau) Nakai]을 대상으로 몇 가지 재배 조건에 대한 생육 차이를 확인하였다. 국립생물자원관으로부터 분양 받은 세 종의 종자는 휴면 여부와 발아 적온을 확인하기 위해 종자를 페트리디쉬에 파종한 후 15, 20, 25, 30℃(명 또는 암조건) 및 25/15℃(16/8h, 명/암) 조건에 배치하였다. 재배실험은 유리온실에서 수행되었으며, 토양에 파종 후 4주간 육묘한 다음 균일한 생육상태의 묘를 7cm 포트에 이식하여 실험의 재료로 사용하였다. 토양실험은 시판 원예용상토와 마사토를 혼합하여 사용하였으며, 비율을 1:1, 2:1 및 3:1로 조성하였다. 차광 환경은 55, 75% 차광과 무차광 조건으로 달리 하였으며, 추비는 재배 6, 8, 10주차에 500, 1,000ppm의 하이포넥스(NPK 7-10-6) 용액을 엽면시비 하였다. 토양실험을 제외한 모든처리구에서는 원예상토 단용을 사용하였으며, 이식 후 12주간 재배하였다. 발아 실험 결과, 참김의털은 명조건에서 25/15와 15℃를 제외하고 발아율이 10% 이하로 조사되었으며, 암조건에서 온도가 증가할수록 발아율이 감소하였다. 청사초는 모든 온도에서 90%이상 발아하였으며, 암조건의 경우 발아율이 10% 이하로 조사되어 광발아성 종자로 확인되었다. 골풀은 실험이 진행된 30일 동안 모든온도에서 발아하지 않았으나, 재배실험을 위해 토양에 파종된 골풀은 파종 약3주 이후 발아가 관찰되었다. 재배실험 결과, 참김의털과 청사초의 경우 2:1로 혼합한 토양에서 엽수와 분얼수, 생체중 등이 가장 높게 조사되어 관상적 가치가 높았으며, 골풀은 3:1의 혼합토양에서 생육이 가장 우수하였다. 차광은 세 종 모두에게서 생육에 부정적인 영향을 미쳤으며, 청사초와 골풀은 500ppm의 하이포넥스를 시비하였을 때 생육이 촉진되었다.

• Industry Promotion Research
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• v.9 no.2
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• pp.29-35
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• 2024

Recently, the Korean financial market has implemented a ban on unleveraged short selling, and leveraged short selling, which involves selling borrowed securities, is called general short selling. This study sought to come up with improvement measures to revitalize short selling from the perspective of individual investors. Short selling refers to selling stocks you do not own in the stock market, predicting that the stock price of the stock will fall, and borrowing stocks to sell them. Based on the results of this study, the short selling market's growth and improvement plans are as follows. First, a plan must be developed to expand short selling opportunities for individual investors. In the domestic short selling market, including KOSPI and KOSDAQ, foreign and institutional participants account for more than 95% of the market, and individual investors are very small. Therefore, its expansion is inevitable. Second, monitoring and punishment for unfair short selling transactions must be strengthened. Representative improvement measures that can minimize the side effects of short selling include strengthening monitoring of unfair trading and short selling, and raising the level of punishment. In addition, measures must be taken to further increase the level of punishment for short selling related to unfair transactions. Third, the short selling reporting and disclosure system needs to be improved. In the case of Korea, short selling transactions are not yet as active as in developed countries, but there is a need to expand the disclosure system to strengthen market transparency in preparation for future short selling transactions becoming more active. In conclusion, it is reported that if short selling regulations are excessively strengthened, losses may occur in terms of price efficiency and market liquidity, which may ultimately have a negative impact on the market. Therefore, policies related to short selling must be made while taking into account the positive aspects of regulatory effects and the negative impact on the market.

• Applied Biological Chemistry
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• v.43 no.4
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• pp.291-297
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• 2000

This study was conducted to find out the environmental factors affecting the differences in the half-life of the insecticide cyfluthrin in soil between field and laboratory tests carried out in 1998. Degradation and leaching of cyfluthrin in soil were examined under various environmental conditions that were considered to affect the residuality. Cyfluthrin was degraded 1.9 times faster in non-sterilized soil than in sterilized soil and 1.2 times at $25^{\circ}C$ than at $15^{\circ}C$. The half-lives of cyfluthrin were 61.4 days under the dark condition and 4.5 days under sunlight, and those were 11.8 days under the open condition and 23.8 days under the closed condition. The half-lives of the authentic compound and the commercial product of cyfluthrin were 15 and 1 day in the field test and 26 and 3 days in the laboratory test, respectively. Cyfluthrin was rapidly degraded with an increase in soil moisture content and decomposed faster in the alkaline solution of pH 12 than in the acidic solution of pH 3, but the half-life of cyfluthrin did not make any difference between pH 6.4 of the field test soil and pH 5.6 of the laboratory test soil. Cyfluthrin was immobile in soil from the results that $81{\sim}94%$ of the initial amount remained in the $0{\sim}2\;cm$ layer of the soil column regardless of the amount and time of rainfall after the chemical treatments. From viewing the abovementioned results, soil moisture content, sunlight and formulation type affected greatly soil microbes and volatilization affected slightly, and temperature, pH and rainfall did not affect the big difference in the half-life of cyfluthrin in soil between the field and laboratory tests in the year of 1998.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.129-145
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• 2019

For the design of composite breakwater as representative one of the coastal and harbor structures, it has been widely discussed by the researchers about the relation between the behavior of excess-pore-water pressure inside the rubble mound and seabed caused by the wave load and its structural failure. Recently, the researchers have tried to verify its relation through the numerical simulation technique. The above researches through numerical simulation have been mostly applied by the linear and nonlinear analytic methods, but there have been no researches through the numerical simulation by the strongly nonlinear mutiphase flow analytical method considering wave-breaking phenomena by VOF method and turbulence model by LES method yet. In the preceding research of this study, olaFlow model based on the mutiphase flow analytical method was applied to the nonlinear interaction analysis of regular wave-composite breakwater-seabed. Also, the same numerical techniques as preceding research are utilized for the analysis of irregular wave-composite breakwater-seabed in this study. Through this paper, it is investigated about the horizontal wave pressures, the time variations of excess-pore-water pressure and their frequency spectra, mean flow velocities, mean vorticities, mean turbulent kinetic energies and etc. around the caisson, rubble mound of the composite breakwater and seabed according to the changes of significant wave height and period. From these results, it was found that maximum nondimensional excess-pore water pressure, mean turbulent kinetic energy and mean vorticity come to be large equally on the horizontal plane in front of rubble mound, circulation of inflow around still water level and outflow around seabed is formed in front of rubble caisson.