• 한국해양학회지
• /
• v.28 no.2
• /
• pp.101-106
• /
• 1993

A simple three-dimensional cubic model is applied to the formation of the Yellow Sea Cold Water Mass in Summer. We studied how the tidal mixing and the Kuroshio Water Mass affect the formation of the Yellow Sea cold Water. The tidal mixing effect is parameterized into the vertical diffusion coefficient because of the technical difficulties in the numerical model In this study, the thermal front along the coast could be formed only by the tidal mixing effect. However, the southern front of the Yellow Sea Cold Water Mass has to consider the warm Kuroshio water. the resultant shows the opposite temperature distribution in upper layer and lower layer. the center of the model is warmer in the upper layer and colder in the lower layer than the coast. The resultant circulation pattern is also reverse, clockwise circulation in the upper layer and counter-clockwise circulation in the lower layer.

• 한국해양학회지
• /
• v.13 no.1
• /
• pp.1-8
• /
• 1978

A seismic reflection Survey was carried out in the offshere area between Geoje Island and Namhae Island, utilizing the echosounder with the frequency 28KHz and thd Uniboom with the filter band 800∼2000Hz. The results show the submarine topography, sedimentary layer structure and the depth distribution of the base rock. The water depth of the sea in the survey area is less than 80m; up to 40m contour line the sea bottom surface has a slight dip(about 1/1000), while in the zone deeper than 40m the bottom topography has a irregular relief. The thickness of the whole sedimentary deposit is about 20∼70m and divided into 3 layers: Upper layer(A layer) with horizontal laminae, intermediate layer(B layer) with cross-bedding and groove structure, and lower layer(C layer) not showing any sedimentary structure on the seismic reflection profile. The surface of the base rock is deeper gradually in the south-eastern part of the survey area and extends to 140m depth. The vertical sediments sequences, composed of B layer and A layer, show the type of transgressive sequences. It is interpreted that B layer was formed at one period when the sea level was lower 40∼60 than the present and ince then, following the rising of the sea level, A layer was deposited.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.444-448
• /
• 2007

자연하천에서 단위구간(측선)의 연직선상 평균유속산정을 위한 일반적인 측정방법으로는 표면유속법, 1점법, 2점법, 3점법, 4점법, 5점법, 6점법, 연직 유속분포법 등이 있으며, 본 연구에서는 지난 1년간 낙동강유역 이안, 신풍, 성덕(무계), 성덕(보현)지점에서 회전식유속계로 측정한 유속자료를 이용하여 측선별 연직분포곡선을 작성한 후 측정지점 횡단면상 수심이 얕은 양안과 상류 제약조건(수풀 또는 돌출된 바위 등)으로 인해 측선의 흐름이 왜곡되는 지점을 제외한 측선별 연직유속분포곡선을 평균하여 지점별 대표 연직유속분포곡선을 작성하였다. 지점별 대표 연직유속분포 곡선을 작성하여 평균유속을 산정한 값을 기준으로 하천유량 측정시 일반적 평균유속 산정방법인 1, 2, 3점법 및 표면유속법에 대한 변동계수를 분석한 결과 1점법은 0.064, 2점법은 0.027, 3점법은 0.043, 표면유속법은 0.126으로 1, 2, 3 점법에서는 지점별 변화가 비교적 작게 나타났으며 표면유속법에서는 유량측정 지점별 변화가 큰 것으로 나타났다. 또한, 낙동지점에서 ADCP를 이용한 유량측정시 수집된 측선별 연직유속분포자료를 이용, 측정지점의 유량별 대표 연직유속분포 곡선을 작성, 실제 하천유량측정에 널리 쓰이고 있는 평균유속 측정방법을 비교 분석하였다. 분석결과, 1점법에서는 평균유속대비 1.076, 2점법에서는 1.026, 3점법에서는 0.051로서 2, 3점법이 대체로 양호한 결과를 보이며 이는 Hulsing 등의 연직유속분포곡선을 이용하여 계산한 1점법에서 1.020, 2점법, 1.010, 3점법 1.015의 결과 추세와도 일치하였다.

• Steel and Composite Structures
• /
• v.34 no.4
• /
• pp.511-524
• /
• 2020

In this research, a simple four-variable trigonometric integral shear deformation model is proposed for the static behavior of advanced functionally graded (AFG) ceramic-metal plates supported by a two-parameter elastic foundation and subjected to a nonlinear hygro-thermo-mechanical load. The elastic properties, including both the thermal expansion and moisture coefficients of the plate, are also supposed to be varied within thickness direction by following a power law distribution in terms of volume fractions of the components of the material. The interest of the current theory is seen in its kinematics that use only four independent unknowns, while first-order plate theory and other higher-order plate theories require at least five unknowns. The "in-plane displacement field" of the proposed theory utilizes cosine functions in terms of thickness coordinates to calculate out-of-plane shear deformations. The vertical displacement includes flexural and shear components. The elastic foundation is introduced in mathematical modeling as a two-parameter Winkler-Pasternak foundation. The virtual displacement principle is applied to obtain the basic equations and a Navier solution technique is used to determine an analytical solution. The numerical results predicted by the proposed formulation are compared with results already published in the literature to demonstrate the accuracy and efficiency of the proposed theory. The influences of "moisture concentration", temperature, stiffness of foundation, shear deformation, geometric ratios and volume fraction variation on the mechanical behavior of AFG plates are examined and discussed in detail.

• Journal of Powder Materials
• /
• v.14 no.5
• /
• pp.281-286
• /
• 2007

Ordered $L1_0$ to FePt nanoparticles are strong candidates for high density magnetic data storage media because the $L1_0$ phase FePt has a very high magnetocrystalline anisotropy $(K_u{\sim}6.6-10{\times}10^7erg/cm^3)$, high coercivity and chemical stability. In this study, the ordered $L1_0$ FePt nanoparticles were successfully fabricated by chemical vapor condensation process without a post-annealing process which causes severe particle growth and agglomeration. The $Fe_{50}Pt_{50}$ nanopowder was obtained when the mixing ratio of Fe(acac) and Pt(arac) was 2.5 : 1. And the synthesized FePt nanoparticles were very fine and spherical shape with a narrow size distribution. The average particle size of the powder tended to increase from 5 nm to 10 nm with increasing reaction temperature from $800^{\circ}C$ to $1000^{\circ}C$. Characterisitcs of FePt nanopowder were investigated in terms of process parameters and microstructures.

• The Korean Journal of Quaternary Research
• /
• v.22 no.1
• /
• pp.28-36
• /
• 2008

The present study has focused on the environmental changes and evidences for sedimentation in the Lake Khuvsgul catchment during the Holocene period, inferred from short core sediment (BO03) from the eastern shore of Borsog Bay, which were analyzed in order to review records of the Holocene climatic evolution and Holocene history in Northern Mongolia. For the purpose of reconstruction of natural phenomenon that occurred in the lake catchment system during the Holocene, physical and chemical properties including HCl-soluble material, biogenic silica, organic matter and grain size distribution of minerals in the core sediments have been analyzed in this study. The vertical variations in composition for these properties show distinctly that five lines of paleoenvironmental evidence occurred in the lake catchment during the Holocene. A modified age model resulting from AMS carbon dating for the BO03 core sediment shows timings of these environmental events at 9.5 Kyr BP, 8.0 Kyr BP, 5.6 Kyr BP and 3.2 Kyr BP, respectively. Paleoenvironmental changes in the Lake Khuvsgul catchment system during the Holocene highlight distinctive features of the hydrological regime and geomorphologic evolution in the lake catchment due to regional landscape and global climatic changes corresponding with the Holocene optimum and thermal optimum. In particular, the change of hydrologic regime based on the sedimentological evidence has been caused by not only overland flow due to melting water, but also base flow due to thick permafrost around Khuvsgul region.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.24 no.1
• /
• pp.36-47
• /
• 2012

In this study, the control performance of resonator was reviewed through numerical analysis and 3-dimensional hydraulic model experiments by attaching the resonator suggested in the existing studies to the openings of rectangular harbor and breakwater placed in a straight line to reduce short-period waves. In the numerical analysis, linear analysis method of singularity distribution method based on vertical-line Green function and full non-linear analysis method by 3D-NIT model were applied, and the validity of the numerical analysis methods was verified through comparative analysis between results of hydraulic experiments and numerical analysis results. In addition, effectiveness of the resonator was confirmed by reviewing its control performance on the short-period waves through review on the comparison with the case in which the resonator is not attached.

• Economic and Environmental Geology
• /
• v.17 no.2
• /
• pp.109-114
• /
• 1984

The geophysical implications of the observed heat flow in the Korean Peninsula are examined. The Peninsula can be devided into two typical regions of high (Zone 1) and normal heat flows (Zone 2), and anomalous sharp change of heat flow between two zones is noteworthy. Zone 1 (southeastern coast of the Peninsula) to be connected to the East Sea (=Japan Sea) of high heat flow region corresponds with the region of late-Mesozoic to Tertiary igneous activity. With the radioactive elements concentrated in the crust, the observed heat flow in Zone 2 can be almostly explained. While, only a half of the heat flow in Zone 1 is explained. As a possible explanation of high heat flow in Zone 1, partial melting in the lower crust is examined. The temperature of $800-900^{\circ}C$ calculated at the bottom of the crust excludes the possibility of partial melting or magma generation in the crust. Alternatively, a remaining thermal effect of late-Mesozoic to Tertiary igneous activity is considered. However, it appears that the thermal effect already disappeared and that the vertical temperature distribution reached at steady state 30 MY ago (= 10 MY after the igneous activities came to an end). After all, the existence of some other effective heat transfer in Zone 1 is strongly suggested. The high heat flow to be same kind of anomalous one of the East Sea can be recognized as a result of the trench-back-arc thermal flux. The plate subduction in the Japan Trench will generate an induced flow above the slab of the East Sea, a typical back-arc basin, and hence the induced flow will heat the surrounding lithosphere.

• Economic and Environmental Geology
• /
• v.30 no.4
• /
• pp.341-352
• /
• 1997

Retention ponds have been dug along some of the motorways in France to minimize environmental pollution by keeping pollutants from spreading over the surrounding area. In order to study heavy metal pollution and diagenetic behaviour of sediments, eight core samples were collected from the bottom of a retention pond located along the A-71 motorway in Sologne. The metal concentrations in interstitial waters and extractable metal concentrations in sediment layers using sequential chemical extraction method were determined. The depth distributions of Pb, Zn and Cd concentrations in interstitial water and particulate sediments were studied, and distribution coefficients (KD) were also determined to investigate the environmental mobility of these elements. In addition. the index of geoaccumulation and the Fe-normalized enrichment factor were calculated to differentiate the natural accumulation from the anthropogenic pollution. The vertical concentration profiles of heavy metals in core sediments indicate that surface enrichments (0~2 cm) of Pb, Zn, Cd and organic carbon were always observed at each core sample, due to the early diagenesis. However, the major factor contributing to the accumulation of Cd at the sediment surface is attributed to the dissolution of Cd from polluted roadside soil during periods of rainstorms and its subsequent redeposition on the sediment surface after being carried to the retention pond. A comparison of the KD values indiactes that a decrease in the KD values for Pb and Zn was observed with depth while KD values for Cd increase. According to the KD values. the relative mobility of studied metals was determined as following: Mn>Zn>Cd>Pb, for the upper layer, and Mn>Cd>Zn>Pb, for the lower layers.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.11 no.5
• /
• pp.60-71
• /
• 2008

Through analyzing the specific physicochemical alterations in depth-based soil at reclaimed dredging area, the baseline data were provided for developing the reclaimed dredging area as natural landscape planting sites and ecological-landscape sites based on the soil improvement technology. There was no physical disturbance for 15 to 20 years in Gwangyang Bay reclaimed dredging area after reclamation. Physicochemical examinations of the soil were performed based on the vertical depth. Results of physicochemical analysis such as pH, electric conductivity, total salt contents, silt, clay contents, available phosphorus, calcium, magnesium, sodium, chlorine, and sodium-adsorption ratio showed increasing patterns with the depth while total organic contents, total nitrogen, and sand showed decreasing patterns. Potassium as an exchangeable cation, showed similar distribution patterns between the shallow and deep soil. This result strongly implied that long-term exposure to natural rainfall in reclaimed dredging area altered soil characteristics related to salinity. This research demonstrated that there were no remarkable differences in physicochemical characteristics at soil depth and groundwater table height, suggesting a baseline data for developing reclaimed dredging area. Additional investigation is required for different reclaimed dredging areas. Also, additional monitoring and examination are need on plant communities and time variable alteration in the soil to test the feasibility of reclaimed dredging areas as natural landscape planting sites and ecological-landscape sites.