• Title/Summary/Keyword: 모래상자

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Annual Transfer of $^{90}Sr$ to Rice from Paddy Soils Collected around Yonggwang and Ulchin Nuclear Power Plants (영광 및 울진 원전 주변 논 토양으로부터 벼로의 년차별 $^{90}Sr$ 전이)

  • Lim, Kwang-Muk;Choi, Yong-Ho;Park, Hyo-Guk;Kang, Hee-Suk;Choi, Heui-Joo;Lee, Han-Soo
    • Journal of Radiation Protection and Research
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    • v.28 no.4
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    • pp.271-279
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    • 2003
  • Soil blocks were taken into culture boxes from 12 paddy fields within 5 km radii of Yonggwang and Ulchin NPPs and $^{90}Sr$ was applied to the surface water at a pre-transplanting stage and $1{\sim}2$ days before the start of heading. Following the pre-transplanting application, transfer factors were investigated for $2{\sim}4$ years. In the year of application, transfer factors $(m^2\;kg^{-1}-dry)\;of\;^{90}Sr$ applied before transplanting, showing no regionally distinguishable trend, varied with soils by a factor of about 2 with averages of $2.6{\times}10^{-4}$ for hulled seeds and $1.3{\times}10^{-2}$ for straw Transfer factors of $^{90}Sr$ applied shortly before heading were about 2 times greater than those applied before transplanting. Transfer factors tended to decrease with increasing soil pH and exchangeable Ca. Generic values of $^{90}Sr$ transfer factors in the year of deposition were proposed for the Korean paddy fields. In the second year compared with the first year, the transfer factor decreased more in Ulchin soils, which were on the whole higher in sand content, than in Yonggwang soils. For Yonggwang soils as a whole, the annual decrease in transfer factor was well described by an exponential equation with a half-life of about 2.2 years.

Discrete element simulations of continental collision in Asia (아시아 대륙충돌의 개별요소 시뮬레이션)

  • Tanaka Atsushi;Sanada Yoshinori;Yamada Yasuhiro;Matsuoka Toshifumi;Ashida Yuzuru
    • Geophysics and Geophysical Exploration
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    • v.8 no.1
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    • pp.1-6
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    • 2005
  • Analogue physical modelling using granular materials (i.e., sandbox experiments) has been applied with great success to a number of geological problems at various scales. Such physical experiments can also be simulated numerically with the Discrete Element Method (DEM). In this study, we apply the DEM simulation to the collision between the Indian subcontinent and the Eurasian Plate, one of the most significant current tectonic processes in the Earth. DEM simulation has been applied to various kinds of dynamic modelling, not only in structural geology but also in soil mechanics, rock mechanics, and the like. As the target of the investigation is assumed to be an assembly of many tiny particles, DEM simulation makes it possible to treat an object with large and discontinuous deformations. However, in DEM simulations, we often encounter difficulties when we examine the validity of the input parameters, since little is known about the relationship between the input parameters for each particle and the properties of the whole assembly. Therefore, in our previous studies (Yamada et al.,2002a,2002b,2002c), we were obliged to tune the input parameters by trial and error. To overcome these difficulties, we introduce a numerical biaxial test with the DEM simulation. Using the results of this numerical test, we examine the validity of the input parameters used in the collision model. The resulting collision model is quite similar to the real deformation observed in eastern Asia, and compares well with GPS data and in-situ stress data in eastern Asia.

Laboratory Evaluation of Soil Permeability for Sand Using Biot's Acoustic Wave Propagation Theory (Biot 음향 전파 이론을 이용한 실내 사질 시료의 투수계수 산정)

  • Kim, Jin-Won;Song, Chung-Rak
    • Journal of the Korean Geotechnical Society
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    • v.24 no.8
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    • pp.5-12
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    • 2008
  • Biot proposed the frequency dependent formulation for the propagation of elastic waves in saturated media based on the coupled theory mixtures. Based on Biot theory, a special frequency called 'the characteristic frequency' contains unique information of the permeability of soils. The characteristic frequency is measured from I/Q (inverse quality factor) versus frequency curve by an acoustic sweep test, and the permeability of soils is computed from Biot equation. In this paper, laboratory tests are performed at The University of Mississippi using a large test box. The measured characteristic frequency is consistently obtained at 3500 Hz for mortar sands. The computed permeability of mortar sands based on Biot equation turned out 2.01 $10^{-4}m/sec$, while the permeability from the laboratory constant head test turned out 1.49 $10^{-4}m/sec$. This paper addresses the theoretical background and experimental procedure of this technique.

Quality of Yellow Poplar (Liriodendron tulipifera) Seedlings by the Method of Seedling Production (백합나무 양묘방법에 따른 묘목품질 비교)

  • Ryu, Keun-Ok;Song, Jeong-Ho;Choi, Hyung-Soon;Kwon, Hae-Yun;Kwon, Yong-Rak
    • Journal of Korean Society of Forest Science
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    • v.96 no.3
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    • pp.307-316
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    • 2007
  • Yellow poplar (Liriodendron tulipifera L.) has low germination rate relatively other species, so the seedling production of Yellow poplar is a hard task. Accordingly this study was conducted to determine the optimal germination conditions for healthy seedling production and to promote survival rate after afforestation. Gemination percentage was examined at different media and seed covering materials using planting flats in the greenhouse. The best germination percentage was observed in sand for media and compound soil for covering materials. But it was time to transplant, seedlings became a poor character (i.e. height, root length, number of root, dry weight) in sand for media. In order to produce healthy seedlings, each different medium was compounded with TKS-2 (this is a gardening bed soil.) in the ratio 1:1 (v/v.), and compared two conditions. Quality of seedling was better than not mixed TKS-2 into each medium. Transplanting seedlings from greenhouse to nursery grew up rapidly 2 months later (early in August~early in October). Growth amount during two months corresponded to 85.6% and 71.3% in total growth amount of height and diameter at root collar, respectively. In the case of the competition-density effect on yellow-poplar seedlings, direct seedling produced the maximum 35 standard seedlings above 8 mm of root collar diameter per $m^2$, while transplanting seedling produced the maximum 64 standard seedlings per $m^2$. And produced seedlings of two way were significantly different rootlet while axial root and lateral root was not significantly different.