• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.4
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• pp.177-183
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• 1987

The catch by the set net fishery from 1971 to 1985 were analyzed in order to reveal its fluctuation characteristics. Generally, the catch increased from 16,787M/T in 1971 to 84,103M/T in 1985 and showed maximum in 1979 with 99,475M/T of catch. This trend was mainly related to the higher production of file fish which accounts for 64% of the total catch in 1979, and the change of catch statistical classification according to the revising of fishery law in 1976. It was also closely related to the variation of the sea water temperature in coastal area. The main fishing period of the set net fishery appeared from October to November. Catch of the set net fishery was led by that in the southern coast before 1976 and by that in the eastern coast from 1977 to 1980, the tendency changed irregular from 1981. Three groups of fishes could be distinguished by principal component analysis of the annual catch. A group showing steady decreasing tendency was composed of the fishes such as whiting, sand fish, hair tail and anchovy. The another group composed of small alaska pollack, round herring, goby, gizzard shad, sand lance and file fish revaled an increasing tendency. The other fishes did not show any annual tendency.

• Journal of the Korean Geotechnical Society
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• v.28 no.8
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• pp.43-53
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• 2012

In the conventional design of a piled raft, the axial resistance offered by the raft itself is typically neglected and only that of the group pile is accounted in estimating the total axial resistance of the piled raft. As a consequence, piled rafts are usually designed conservatively by neglecting the raft resistance. In this study, a series of centrifuge model tests have been performed to compare the axial behavior of a group pile with that of a piled raft (both having 16 component piles with an array of $4{\times}4$) in sands with different relative densities and in clays with different preconsolidated pressures. The test results revealed that, with respect to the allowable settlement of 25 millimeters for bridge foundations, the piled raft resistances were greater than those of the group pile by 13% for dense sand, by 22% for loose sand, by 30% for stiff clay, and by 22% for soft clay. Furthermore, the ratio of piled raft resistance to group pile resistance increased as the settlement increased.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.420-429
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• 2002

The amount of $CO_2$-silicate bonded waste foundry sand(WFS) occurred in Korea is over 800,000 ton per year. WFS, as a by-product, is generated through manufacturing process of foundry may affect our environmental contamination, The reason is that WFS has been buried itself not less than 90％ out of total WFS. So, it can give damage on the ground of contamination in soil and underwater. Therefore, it is necessary to establish the method recycling WFS because of being intensified waste management law. In this study, we performed the research with respect to harmful component analysis, the qualities of WFS mortar and concrete mixed with WFS. As the results the specific gravity of WFS is the same as that of natural aggregate while unit weight and percentage of solids of WFS are smaller than those of it. But it is found that WFS can be used by substituting WFS for natural aggregate after control of poor grade of WFS. The flowability of mortar and concrete with WFS is inferior to those of natural aggregate, and the setting time of concrete with WFS is faster than that with only natural aggregate, On the contrary, the bleeding of concrete with WFS is shown good result, and compressive and tensile strength of concrete substituted WFS for 30％ are higher than those with only natural aggregate regardless of elapsed time.

• Korean Journal of Environmental Agriculture
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• v.29 no.1
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• pp.1-6
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• 2010

Organic farming system in rice paddy is rapidly expanding in Korea. This study was to find out optimum japonica rice cultivars for organic farming. A field research was conducted to evaluate the characteristics of japonica rice cultivars under no-tillage paddy at Doo-ryangmyeon, Sacheon, Gyeongsangnam-do, Korea. The experimental soil was Juggog series (silty clay loam: 56.0% silt, 31.2% clay and 12.8% sand). In experiment, ten lines of Japanese rice cultivars were tested under no-tillage amended with rye (NTR) and no-tillage without cover crop treatment (NTNT). In addition, two Korean japonica rice cultivars as check cultivars were used in this study. The grain yield in NTR was significantly higher in 6.13 Mg $ha^{-1}$ for Kinuhikari, 5.30 Mg $ha^{-1}$ for Komekogane, 5.25 Mg $ha^{-1}$ for Kosihikari, 5.22 Mg $ha^{-1}$ for Mazizbare and 5.12 Mg $ha^{-1}$ for Akitakomachi compared to two Korean rice cultivars (4.57 Mg $ha^{-1}$ for Hwayoungbyeo and 4.00 Mg $ha^{-1}$ for Ilmibyeo) in that order. While, grain yield in NTNT was significantly higher in 4.90 Mg $ha^{-1}$ for Akitakomachi 3.81 Mg $ha^{-1}$ for Hinohikari, 3.74 Mg $ha^{-1}$ for Umezkusi, 3.67 Mg $ha^{-1}$ for Kosihikari and 3.54 Mg $ha^{-1}$ for Dondokuri compared to 3.02 Mg $ha^{-1}$ for Ilmibyeo and 2.36 Mg $ha^{-1}$ for Hwayoungbyeo, respectively. The number of panicle per $m^2$ and grain number per panicle were indispensible for increasing the yield of rice. These results were able to find out optimum japonica rice cultivar Akitakomachi for organic farming in no-tillage paddy.

• Journal of the Korean Geotechnical Society
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• v.28 no.10
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• pp.27-40
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• 2012

In the design of a piled raft, the axial resistance is offered by the raft and group piles acting on the same supporting ground soils. As a consequence, pile - soil - raft and pile - soil interactions, occurring by stress and displacement duplication with pile and raft loading conditions, act as a key element changing resistances of the raft and group piles. In this study, a series of centrifuge model tests have been performed to compare the axial behavior of group pile and raft with that of a piled raft (having 16 component piles with an array of $4{\times}4$) in sands with different relative densities. The test results revealed that the increase of settlement resistance occurs separately with settlement by group pile - soil interactions. The axial resistance of group piles (at piled raft) increases by group pile - raft (pile cap) interactions and that of raft (at piled raft) decreases by group pile - raft (pile cap) interactions.

• 한국해양학회지
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• v.28 no.2
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• pp.114-120
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• 1993

Numerical method of nonlinear regression was introduced to characterize grain-size distribution more effectively than using the traditional textural parameters. This technique proved critical particularly to multimodal size distributions, as exemplified by samples from Cheju strait continental shelf. Grain-size analysis of samples collected from the Cheju Strait continental shelf reveals that 86% of the grain-size distributions are multimodal. As multimodal grain-size distribution deviates from the statistical (log) normal distribution, the grain-size parameters traditionally used in sediment studies do not describe the distribution efficiently. Therefore, the use of grain-size curves into elementary normal component curves was used. Means and standard deviations of 387 decomposed normal components were decided by a decomposition method (nonlinear least square regression) from 167 size curves of the Cheju Strait sediments. The mean values of decomposed normal components show peaks at 1-3 phi and 8-9 phi size classes. The plot of mean values of the coarse fraction normal components on the map shows a characteristic and complex areal distribution. On the basis of the areal distribution of the mean values of the components and that of isopach of total Plenipotence sediment, the areal distribution of layers composing a transgressive sand of Late Plenipotence age were revealed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.110-117
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• 2011

Seashore landfill projects use undersea pump dredging method for construction of airport and factory site. Coarse grain soil from the dredging is considered for use at inland. West sea shore bottom consists of primarily coarser grained silt-sand and this component contains far more percentage than is the case with East sea and South sea area. This soil shows very different characteristic at consolidation and compaction behavior. This research targets to utilize this type of dredging soil. Test specimen is from West sea (Saemangum) dredged soil landfill site. Model analysis is done for getting prediction of original soil relative density and N-value from dynamic compaction energy variance. Dynamic compaction energy is calculated for efficient foundation design.

• Journal of the Korean Geosynthetics Society
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• v.23 no.1
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• pp.1-7
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• 2024

In this study, a selecvively block barrier was developed to prevent the spread of contaminants (TPH, Phenol) in the ground only when contamination occurs. The materials were used Jumunjin sand, bentonite, polyolefin elastomer and spill hound marine. First, the properties and environmental hazards characteristics of materials were analyzed for evaluated their usability. Then, the possibility of use as a barrier material was confirmed by analyzing the water permeability characteristics that change after 24 hours of contact with contaminants. As a result of the analysis, the pH of each component was similar to the general groundwater pH range. In addition, the toxicity characteristics and the possibility of dissolution of hazardous substances, it was determined that there was no environmental hazard as the content was below the regulation value. Lastly, when comparing the permeability coefficient before and after contact with the contaminant, the permeability coefficient of approximately α × 10^-3cm/sec before contact was reduced to α × 10^-6cm/sec after contact with the contaminant.

• Explosives and Blasting
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• v.22 no.1
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• pp.33-43
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• 2004

In this study, a comparison was made between the resulting behaviors of scaled model test and particle flow analysis for blasting demolition of a reinforced concrete structure. For the test and analysis, a progressive failure of a five-story structure was considered. The dimension analysis was carried out to properly scale down the real structure into the laboratory size. The test model was made of the mixture of gypsum, sand and water along with soldering lead to analogy reinforcing steel bars. The ratio of mixing components was chosen to best represent the scaled down strength and deformation modulus. The columns and girders of the structure were precasted in the laboratory and assembled right before the blasting test. The numerical analysis of the blasting demolition was carried out using PFC2D (Particle Flow Analysis 2-Dimension by Itasca). The results of the blasting of concrete lahmen structure showed roughly identical demolition behavior between scaled model test and numerical test. For the blasting of the reinforced concrete structure, the results were more identical and closer to the real demolition behavior, since the demolition behavior was better represented in this case due to the increased tensile strength of the component.

• Korean Journal of Ecology and Environment
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• v.46 no.3
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• pp.343-359
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• 2013

In order to understand shoreline environment characteristics of Korean reservoirs, the interrelationships between environmental factors of geomorphology, hydrology, water quality and shoreline soil were analyzed, and the reservoir types were classified according to their environmental characteristics in the 35 reservoirs selected by considering the purpose of dam operations and annual water-level fluctuations. Geomorphological and hydrological characteristics of reservoirs were correlated with the altitude and the size scale of reservoirs. The annual range of water level fluctuation showed a wide variation from 1 m to 27 m in the various reservoirs in Korea. The levels of eutrophication of most reservoirs were mesotrophic or eutrophic. From the result of the soil texture analysis, sand contents were high in reservoir shorelines. Range, frequency and duration of water-level fluctuation were distinctive from the primary function of reservoirs. Flood control reservoirs had a wide range with low frequency and waterpower generation reservoirs had a narrow range with high frequency in the water-level fluctuation. According to the result of CART (classification and regression tree) analysis, the water quality of reservoirs was classified by water depth, range of water-level fluctuation and altitude. The result of PCA (principal component analysis) showed that the type of reservoirs was classified by reservoir size, water-level fluctuation, water quality, soil texture and soil organic matter. In conclusion, reservoir size, the water-level fluctuation, water quality and soil characteristics might be major factors in the environment of reservoir shorelines in Korea.