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Physical and Chemical Characteristics of Dokdo Soil
이길성,추연식 한국생태학회 2009 Journal of Ecology and Environment Vol.32 No.4
To understand the properties of soil in Dokdo, we collected soil samples from 12 locations on Seodo and 23 locations on Dongdo, in Dokdo of Gyeongsangbuk-do Province in 2007-2008 and analyzed the soil’s physical and chemical characteristics. Sand comprises the largest component (49.37%) of Dokdo soil, followed by silt (40.70%) and clay (9.93%). The soil structure consists mostly of sand loam, followed by loam and silt loam. The pH level of soils from Dokdo varied dramatically among sampling sites and seasons, ranging from 3.36 to 8.02. The total ion content of Dokdo soil also varies greatly among survey places and periods, but in general the total ion content was high in summer when vegetation develops, and low in spring. The exchangeable cation contents of the soil showed low levels in samples where the soil pH was low, including habitats dominated by Agropyron tsukushiense var. transiens and Echinochloa crus-galli, whereas the exchangeable cation contents were high where the organic contents were high, as in habitats dominated by Liriope platyphylla and Artemisia japonica subsp. littoricola. Soil N contents varied greatly among survey sites and higher N contents were found in soil inhabited by Chenopodiaceous plants than in habitats inhabited by other plants. The substantial differences in phosphorus contents among sites were related to excrement of black-tailed gulls. To understand the basic physical and chemical features of the soil on Dokdo, it will be necessary to conduct seasonal and long-term research on soil pH, ion contents, organic contents, N and P, as well as obtaining precise data from samples collected at different depths.
Free Surface Flow in a Trench Channel Using 3-D Finite Volume Method
이길성,박기두,오진호 한국수자원학회 2011 한국수자원학회논문집 Vol.44 No.6
In order to simulate a free surface flow in a trench channel, a three-dimensional incompressible unsteady Reynolds-averaged Navier-Stokes(RANS) equations are closed with the model. The artificial compressibility(AC) method is used. Because the pressure fields can be coupled directly with the velocity fields, the incompressible Navier-Stokes(INS) equations can be solved for the unknown variables such as velocity components and pressure. The governing equations are discretized in a conservation form using a second order accurate finite volume method on non-staggered grids. In order to prevent the oscillatory behavior of computed solutions known as odd-even decoupling, an artificial dissipation using the flux- difference splitting upwind scheme is applied. To enhance the efficiency and robustness of the numerical algorithm, the implicit method of the Beam and Warming method is employed. The treatment of the free surface, so-called interface-tracking method, is proposed using the free surface evolution equation and the kinematic free surface boundary conditions at the free surface instead of the dynamic free surface boundary condition. AC method in this paper can be applied only to the hydrodynamic pressure using the decomposition into hydrostatic pressure and hydrodynamic pressure components. In this study, the boundary-fitted grids are used and advanced each time the free surface moved. The accuracy of our RANS solver is compared with the laboratory experimental and numerical data for a fully turbulent shallow-water trench flow. The algorithm yields practically identical velocity profiles that are in good overall agreement with the laboratory experimental measurement for the turbulent flow.
훈증제 ethylene oxide가 문화재의 색도에 미치는 영향
이길성,박병빈,최기영 한국환경보건학회 2002 한국환경보건학회지 Vol.28 No.5
It is well-known method to use Ethylene Oxide (ETO) as a fumigant to preserve cultural heritage from the attack of some bacteria and insects. In this article, we investigated color change of some cultural material upon treating ETO. The cultural material was selected from Korean paper (hanji), ancient books, blue prints. pigments (DA. DB, DC. DO. DE and OF), hemp cloths. and colored pictures (DG. DH. 야, DJ, OK). The AE value in chromaticity coordinates for each item was obtained upon treatment with ETO at concentration of 200, 250, 380. 500, 710 g/m³ respectively. The AE value was derived from the equation of L*ab with the data checked 24 hr. 48 hr, and 72 hrs respectively. The Korean papers(lranji) showed slightly change in color by Llli 0.8. In the ca~e of ancient books. it showed AE 2.91 which was easily distinguishable with the naked eyes. For the almost 73%of blue prints. the value of AE was as much as more than 4.0 that it is recommended not to use. In the case of pigments. the value of AE was ranged from 0.15 up to 4.0 so that it should be very careful before use. The hemp cloth dyed with natural indigo showed less than 1.00 in AE, while various colored hemp cloth showed wide range of AE from 1.00 to 4.00. Finally. from the fact that the color change was as small as less than 1.00 for the colored pictures, it is thought that treatment with ETO is one of method to be used to this purpose.