• Ocean and Polar Research
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• v.41 no.4
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• pp.265-274
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• 2019

To trace the provenance of fine-grained sediments in response to the growth and retreat of glaciers (i.e., Ross Ice Sheet) that affects the depositional process, various kinds of analyses including magnetic susceptibility, granulometry, and clay mineral composition with AMS ¹⁴C age dating were carried out using a gravity core KI-13-GC2 obtained from the Central Basin of the Ross Sea continental margin. The sediments mostly consist of silty mud to sand with ice-rafted debris, the sediment colors alternate repeatedly between light brown and gray, and the sedimentary structures are almost bioturbated with some faint laminations. Among the fine-grained clay mineral compositions, illite is highest (59.1-76.2%), followed by chlorite (12.4-21.4%), kaolinite (4.1-11.6%), and smectite (1.2-22.6%). Illite and chlorite originated from the Transantarctic mountains (metamorphic rocks and granitic rocks) situated to the south of the Ross Sea. Kaolinite might be supplied from the sedimentary rocks of Antarctic continent underneath the ice sheet. The provenance of smectite was considered as McMurdo volcanic group around the Victoria Land in the western part of the Ross Sea. Chlorite content was higher and smectite content was lower during the glacial periods, although illite and kaolinite contents are almost consistent between the glacial and interglacial periods. The glacial increase of chlorite content may be due to more supply of the reworked continental shelf sediments deposited during the interglacial periods to the Central Basin. On the contrary, the glacial decrease of smectite content may be attributed to less transport from the McMurdo volcanic group to the Central Basin due to the advanced ice sheet. Although the source areas of the clay minerals in the Central Basin have not changed significantly between the interglacial and glacial periods, the transport pathways and delivery mechanism of the clay minerals were different between the glacial and interglacial periods in response to the growth and retreat of Ross Ice Sheet in the Ross Sea.

• Journal of Life Science
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• v.19 no.10
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• pp.1410-1416
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• 2009

The present study aims to examine the effect of turbid water on fishes in streams which branch into a turbid water area (Yeongyang-gun) and a non-turbid water area (Cheongsong-gun), and finally flow into the Imha reservoir. In a comparison of water quality, the chemical status of the water showed higher pH, DO and SS in the turbid water area than in the non-turbid water area. Also, high density of clay minerals such as vermiculite (V) and illite (I), which is from clay mineral leakage during rainfall, was detected in turbid water, resulting in an increase of turbidity. Fishes inhabiting the turbid water showed irregular spaces in gill lamella, cell separation, edema, and clubbing in epithelial tissues. Also, the gill surface showed roughness and plenty of muddy debris substances inside the gills. The Bowman's space was expanded because of contraction of the glomerulus in the Bowman's space of the kidney tissues. Antioxidant enzymes such as SOD, CAT, GPX, and GST showed higher activities in the specific tissues, muscles and kidney, of fishes living in turbid water than in the non-turbid area. We suggested that; first, the antioxidant activities were increased due to removal of harmful radicals generated in fish bodies in the turbid water area, second, long-time exposure of these histological changes in the tissues might have induced secondary lesion accompanying the inaccurate physiological constancy of fishes.

• Korean Journal of Environment and Ecology
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• v.29 no.5
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• pp.785-790
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• 2015

As an alternative to large-scale clear cutting silviculture, strip clear cutting (SC) is being considered as a system compatible with ecological conservation and forest regeneration. In South Korea, application and effectiveness of SCC in varying forest types were rarely found. In this study, under the subject of strip clear cutting lands of pinus densiflora forest at Samcheok, Gangwon-do Province, the developmental aspect of low vegetation prior to and after deforestation and the correlation between environmental factor and pine regeneration were analyzed. The cover rate of understory vegetation was appeared to be increased after deforestation and rapidly increased two years after deforestation, and it was evaluated to be affected by vigorous tree species and photophilic species. From the perspective of relative importance value, Quercus mongolica, Artemisia keiskeana, and Rubus crataegifolius that influence the cover rate showed the inclination of continuous growth. The diversity of species showed increment inclination as well due to introduction and settlement of early transient species. As a result of analyzing the correlation between vegetation and environmental factor and generation of pine tree size, the soil exposure rate, intensity of light, and canopy openness showed positive relationship, and the understory vegetation cover and woody debris cover rate showed negative relationship.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.163-176
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• 2007

Landslides which is one of the major natural hazard is defined as a mass movement of weathered material rock and debris due to gravity and can be triggered by complex mechanism. It causes enormous property damages and losses of human lift directly and indirectly. In order to mitigate landslide risk effectively, a new method is required to develope for better understanding of landslide risk based on the damaged cost produce, investment priority data, etc. In this study, we suggest a new evaluation method for slope stability using risk analysis. 30 slopes including 10 stable slopes, 10 slopes of possible failure and 10 failed slopes along the national and local roads are examined. Risk analysis comprises the hazard analysis and the consequence analysis. Risk scores evaluated by risk analysis show very clear boundaries for each category and are the highest for the failed slopes and the lowest for the stable slopes. The evaluation method for slope stability suggested by this research may define the condition and stability of slope more clearly than other methods suggested by others.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.315-324
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• 2016

Because of a fissility characteristics of shale in the Gyoungsang super-group, it breaks down to debris when daylighted by construction work and causes a slope unstability. To assess the durability property of shale, a series of slake durability tests was conducted by controlling test conditions such as shape of specimen, number of specimen, revolution speed, revolution number, drying temperature and pH of submerging liquid. For the specimen shape, cube one showed relatively lower durability index than cuboid and/or fan shape one. The test with the more number of specimens showed the less durability index because of a higher friction among specimens in the drum. The durability index is linearly decreased by increasing the total number of revolution, while the revolution velocity could not affect the index. And the durability index is also decreased by increasing the drying temperature of specimen and by decreasing the pH of submerging liquid. Because the durability index of shale is almost similar to that of crystalline rocks, the disintegration characteristics of shale could not be assessed by the slake durability test recommended by ISRM, and thus a new test method by changing the total revolution number may be required for the shale having fissility characteristics.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.3 no.3
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• pp.12-19
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• 2000

The purpose of this study is to evaluate the channel changes according to the temporal and spatial distribution of the deposition area by the vegetation invasion in Kyesung-river. The deposition area mainly occurred by landslide and debris flow from the headwater channel. And also the movement of subsequent downstream depends upon the site of deposits by a varity erosional processes. As the age of deposition area is older, it had a tendency to stable by plant invasion relatively. The vegetations grown in deposition area were very effective to estimate a historical deformation process of river-bed occurred by landslide. The vegetations around deposition area consisted of the same as tree species grown in forest area of circumference like Pinus densiflora, Styrax japonica, Quercus acutissima and Salix gracilistyla. If the torrential stream is flooding, the deposition area of 1 to 5 years can be change to the channel easily. Deposition area of 11 to 23 years had a high river-bed because it passed long time since deposited, and amount of sedimention is much more in wide than in narrow channel. It is consider that the change of channel had many influenced by the span of survial time, scale and movement frequency of deposition area after the vegetation invasion.

• Korean Journal of Poultry Science
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• v.30 no.1
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• pp.41-47
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• 2003

This study was conducted to investigate the in vivo and in vivo antibiotic effect of crude fucoidan extracted from Hizikia fusiforme, and to investigate any possible structural changes of broiler chick's intestinal villi by the supplementation of fucoidan. Total 84 broiler chicks were randomly assigned to 7 treatments, control and Salmonella typhimurium infection groups. The broiler chicks was infected with Salmonella typhimurium at third days, and antibiotics, fucoidan, dried Hizikia fusiforme, dried Undaria pinnatifida and yeast cell debris was respectively supplemented for each group. Each treatment had 4 chicks with three replications. Extraction yield of crude fucoidan from Hizikia fusiforme was 5.453%. Antibiotic effect of fucoidan was not detected in vitro, inhibition zone and micoorganism growth test. Weight gains of broiler chicks were tend to higher in fucoidan treatment group and yeast cell significance was not found. In in vivo test, the number of viable Salmonella typhimurium was low in the antibiotics and fucoidan treatment groups. The intestinal villi were short in the fucoidan and marine algae treatment groups. The intestinal villi were densely distributed on the large intestinal wall, but the morphology was not different among treatments.

• Korean Journal of Poultry Science
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• v.37 no.2
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• pp.159-165
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• 2010

Field strains of Ornithobacterium rhinotracheale (OR) were tested on their virulence in specific pathogen free (SPF) embryonated chicken eggs and 3-week-old broilers. When infected with three different OR isolates (OR-161, OR-240 and OR-295) through yolk sac infection route, all strains appeared to be highly pathogenic with responsible mortality 66% and 100% within 12 days post infection (DPI). To test the virulence of OR in the commercial broilers, 3 week-old broilers were grouped depends on the inoculation route of OR isolate (OR-295) through five different infection routes; group 1 (IT: intratracheal), group 2 (IM: intramuscular), group 3 (IV: intravenous), group 4 (aerosol) and group 5 [Mixed: NDV (LaSota)+OR aerosol]. Within 5 to 7 days after inoculation, only broilers given NDV+OR were slightly depressed and coughing, and had mild facial redness. Grossly, foamy and yellow-white yogurt like exudate in the air sacs, predominantly in the abdominal air sacs was present. In histology, infiltration of the air sac epithelium and lamina propria by macrophage and polymorphonuclear granulocytes was seen with cell debris and inflammatory cells, correlated with the presence of OR antigen, as demonstrated by immunohistochemistry. Field strains of OR were able to induce high mortality in the embryonated chicken eggs, whereas broilers were less susceptible to OR infection. Interestingly, in the absence of NDV infection, the four groups of OR single infection only different route showed minimal and temporary microscopic air sac lesions. Thus, Newcastle disease virus (LaSota strain) showed triggering effects on the OR infection in chickens.

• Geotechnical Engineering
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• v.10 no.1
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• pp.47-62
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• 1994

It has been well known that the rainfall-triggered rise of groundwater levels is one of the most important factors resulting the instability of the hillside slopes. Thus, the prediction of porewater pressure is an essential step in the evaluation of landslide hazard. This study involves the development and verification of numerical groundwater flow model for the prediction of groundwater flow fluctuations accounting for both of unsatu나toed flow and saturated flow on steep hillside slopes. The first part of this study is to develop a nomerical groundwater flow model. The numerical technique chosen for this study is the finitro element method in combination with the finite difference method. The finite element method is used to transform the space derivatives and the finite difference method is used to discretize the time domain. The second part of this study is to estimate the unknown model parameters used in the proposed numerical model. There were three parameters to be estimated from input -output record $K_e$, $\psi_e$, b. The Maximum -A-Posteriori(MAP) optimization method is utilized for this purpose, . The developed model is applied to a site in Korea where two debris avalanches of large scale and many landslides of small scale were occurred. The results of example analysis show that the numerical groundwater flow model has a capacity of predicting the fluctuation of groundwater levels due to rainfall reasonably well.

• Journal of the Korean Geotechnical Society
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• v.29 no.1
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• pp.49-59
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• 2013

Heavy rainfall intensity may cause shallow slope failures and debris flow by rill erosion and scour on land surface. The paper represents the difference between native soil (weathered soil) and reinforced soil, which is mixed by hardening agent with flyash as main material, for investigating experimental findings of rill erosion and erosion. Results obtained from artificial rainfall simulator show that erosion rate of reinforced soil mixed with hardening agent is reduced by 20% because an amount of eroded soil on slope surface is inversely proportional to the increase of soil strength. For example, rainfall of 45mm (at the elapsed time of 25mins in rainfall intensity of 110mm/hr) triggers rill erosion on native soil surface, but the rill erosion on reinforced soil surface does not even occur at 330mm rainfall (at the elapsed time of 3hrs in rainfall intensity of 110mm/hr). As a result of slope stability analysis, it was found that the construction method for reinforced soil surface would be more economical, easy and fast construction technology than conventional reinforcement method.