• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.s02
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• pp.66-80
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• 1989

Salt injury in rice is caused mainly by the salinity in soil and in the irrigated water, and occasionaly by salinity delivered through typhoon from the sea. The salt concentration of rice plants increased with higher salinity in the soil of the rice growing. The climatic conditions, high temperature and solar radiation and dry conditions promote the salt absorption of rice plant in saline soil. The higher salt accumulation in the rice plant generally reduces the root activity and inhibits the absorption of minerals of rice plant, resulting the reduction of photosynthesis. The salt damages of rice plant, however, are different from different growth stage of rice plants as follows: 1. Germination of rice seed was slightly delayed up to 1.0％ of salt concentration and remarkably at 1. 5％, but none of rice seeds were germinated at 2.5％. This may be due to the delayed water uptake of rice seeds and the inhibition of enzyme activity, 2. It was enable to establish rice seedlings at seed bed by 0.2％ of salt concentration with some reduction of leaf elongation. The increasing of 0.3％ salt concentration caused to the seedling death with varietal differences, but most of seedlings were death at 0.4％ with no varietal differences. 3. Seedlings grown at the nursery over 0.1％ salt, gradually reduced in rooting activity after transplanting according to increasing the salt concentration from 0.1％ up to 0.3％ of paddy field. However, the seedlings grown in normal seed bed showed no difference in rooting between varieties up to 0.1％ but significantly different at 0.3％ between varieties, but greatly reduced at 0.5％ and died at last in paddy after transplanting. 4. At panicle initiation stage, rice plant delayed in heading by salt damage, at meiotic stage reduced in grains and its filling rate due to inhibition of glume and pollen developing, and salt damage at heading stage and till 3 weeks after heading caused to reduction of fertilization and ripening rate. In viewpoint of agricultural policy the overcoming strategy for salt injury is to secure sufficient water source. Irrigation and drainage systems as well as underground drainage is necessary to desalinize more effectively. This must be the most effective and positive way except cost. By cultural practice, growing the salt tolerant variety with high population could increase yield. The intermittent irrigation and fresh water flooding especially at transplanting and from panicle initiation to heading stage, the most sensitive to salt injury, is important to reduce the salt content in saline soil. During the off-cropping season, plough and rotavation with flooding followed by drainage, or submersion and drainage with groove could improve the desalinization. Increase of nitrogen fertilizer with more split application, and soil improvement by lime, organic matter and forign soil addition, could increase the rice yield. Shift of trans-planting is one of the way to escape from the salt injury.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.83-92
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• 2005

The aim of this study was to investigate damage conditions of cut slope structures due to acid rock drainage (ARB) and to assess the acid production potential of various rocks. Acid rock drainage is produced by the oxidation of sulfide minerals contained in coal mine zone and mineralization belt of Pyeongan supergroup and Ogcheon group, pyrite-bearing andesite, and Tertiary acid sulfate soils in Korea. Most of cut slopes producing ARB have been treated with shotcrete to reduce ARD. According to the field observations, ARD had an adverse effect on slope structures. The corrosion of shotcrete, anchors and rock bolts and the bad germination and growth diseases of covering plants due to ARD were observed in the field. The concentration of heavy metals and pH of ARD from cut slope exceeded the environmental standard, indicating a high potential of environmental pollution of surrounding soil, surface water and ground water by the ARD. According to acid base accounting (ABA) of the studied samples, hydrothermally altered volcanic rocks, tuffs, coaly shales, tailings of metallic mine had a relatively high potential of acid production but gneiss and granite had no or less acid production potential. It is expected that the number of cut slopes will increase hereafter considering the present construction trend. In order to reduce the adverse effect of ARD in construction sites, we need to secure the data base for potential ARD producing area and to develop the ARD reduction technologies suitable.

• KCID journal
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• v.18 no.2
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• pp.66-75
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• 2011

Multivariate statistical analysis was applied to 110 dam heightening reservoir to classify the building conditions for waterfront centered around cultivated area using data of land cover, landscape, additional water quantity, local economic, tourism resources, and accessibility related variables. Five factors were extracted through factor analysis based on eigen value criteria of more than one. These five factors together account for 68.2% of the total variance. Characteristics of five factors for the downstream of dam heightening reservoirs are building conditions of waterfront, economic conditions, additional water quantity, eco-tours, and accessibility of tourism resources respectively. Five clusters were classified through cluster analysis based on factor score. The classified result shows that third cluster has remunerative terms for building waterfront.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.11a
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• pp.205-214
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• 1999

In order to investigate the influencing factors of flotation fractionation. flotations were performed at varied conditions. The selectivity of fines fractionation is mainly affected by long fibers flocculating degree and if it were not for sufficient flocculation of long fibers, increase of long fibers loss could not be avoided. The amount of flotation reject totally depends on the stability of forth floated on the stock surface. only the small size fines stabilize the froth as they hinder the drainage of liquid lamella in flotation-froth. Two important factors of flotation conditions are improving the flocculation of long fibers and increasing the amount of flotation reject. Changing a flotation flux or an air-mixing ratio with aims of increasing the flocculation of fibers and reject ratios is in conflict. In order to satisfy the both conditions for reducing long fiber loss and for increasing flotation reject a new fractionation promoter is urgently required.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.4
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• pp.18-26
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• 2000

In order to investigate the influencing factors in flotation fractionation, flotations were performed at varied conditions. The selectivity of fines fractionation was mainly affected by long fiber flocculation degree and if there were not sufficient flocculation of long fibers, more loss of long fibers could not be avoided. The amount of flotation rejects were totally dependent on the stability of froth floated on the stock surface. Only small size fines could stabilize the froth as they hindered the drainage of liquid lamella in flotation-froth. More flotation reject and better flocculation of long fibers were two important factors for improving flotation. Changing a flotation flux or an air-mixing ratio to increase the flocculation of fibers increased long fiber ratio in the reject. In order to satisfy the both conditions of reducing long fiber loss and of increasing flotation reject, search of fractionation promoter is needed.

• Journal of Ecology and Environment
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• v.37 no.2
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• pp.61-67
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• 2014

Mankyua chejuense is a native endangered plant distributed only in Gotzawal, a forested wetland, in Jeju Province, Korea. In order to determine the optimal environmental conditions for the growth and development of M. chejuense, we investigated the above- and below-ground growth responses and survival rate to various soil texture (sand and clay), water regimes (flooding and non-flooding), and $CO_2+T$ (ambient and elevated) conditions. All of the treatments had significant effects on aboveground growth parameters, while only the water regime and $CO_2+T$ treatments influenced belowground growth. The survival rate of M. chejuense was about twice higher under the sand, non-flooding and elevated $CO_2+T$ conditions than clay, flooding and ambient $CO_2+T$ conditions. These results indicate that M. chejuense grows in well-drained sandy soil conditions and elevated $CO_2$ concentration and temperature situations. Thus, there is a need to maintain M. chejuense under constant non-flooding soil conditions by implementing appropriate soil drainage strategies.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.621-626
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• 2005

A major part of permanent way maintenance effort is justified by inadequacies in the track substructure and in particular in drainage conditions, which need to be put right across the entire network. In most cases nowadays, improvements of the substructure can be carried out on rail to a high standard of quality. However, this entails substantial movements of material for the removal of spoil and provision of new material. In the future, recycling of old material on site, and use of geosynthetics, will be necessary to help considerably reduce this volume.

• Proceedings of the Korean Geotechical Society Conference
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• 1992.10a
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• pp.75-86
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• 1992

The elevation of reclamation work in the coastal area for the industrial complex is determined through the investigation and review of marine conditions, drainage plan and fill materials. The embankment to be constructed with crushed stone on the soft soil should be safe against the wave force, immediate and long term consolidation settlement, overturning and sliding due to self-weight and other forces. Because of lack of fill material from the borrow pit, the soft marine clay to be dredged shall be used as the reclamation material. And Paper Drain Board is used as the improvement method for the deep soft clay strata.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.248-254
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• 2015

There has been no previous study on technology development of large capacity drainage pump for rescue sinking ship in the country. The agricultural drainage pump was widely used for rescue sinking ship but this pump has several problems such as efficiency, low displacement and malfunction in winter. Therefore, this paper proposes to solve the problems for swiftly rescue sinking ship and develops the drainage pump system that has $20m^3/min$ mass flow rate specification at suction head 8 m. The centrifugal pump type the most commonly used in the field of naval architecture and ocean engineering was selected and designed based on the requirement specification. The blade design of impeller was derived from the Stepanoff coefficient and requirement specification and used computational fluid dynamics to review the target mass flow rate according to the impeller RPM at design operating conditions. We also performed structure analysis of the impeller to find structurally vulnerable points for the pump in service and completed the theoretical design of drainage pump system.

• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.17-27
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• 2016

Parial drainage characteristics of clayey silt with low plasticity from the west coast (Incheon and Hwaseong) was analyzed using CPTU based existing correlation equations and compulsory replacement method. Generally, the estimated $OCRs={\kappa}{\cdot}((q_t-{\sigma}_{vo})/{\sigma}^{\prime}_{vo})$ using Powell and Quartman(1988) were higher than those obtained by the oeodometer tests. These trends were noticeable for the layers containing a lot of silty and sand soils. The assessment of partial drainage conditions was performed through Schnaid et al. (2004)'s equation; it is based on plotting the normalized cone resistance, $Q_t$ versus the pore pressure parameter, $B_q$ in combination with the strength incremental ratio, $s_u/{\sigma}^{\prime}_{vo}$ to the CPTU data. It is evident that more than half of the data fall in the range where $B_q$ < 0.3, corresponding to the domain in which the partial drainage prevails when testing normally consolidated soils at a standard rate of penetration (2 cm/s). To estimate the replacement depth of clayey silt with low plasticity, back analysis was carried out to evaluate the internal friction angle based on where the design depths are equal to the checked depths using bearing capacity equation. The internal friction angels obtained from the back analysis tended to increase as the plasticity index decreases, which is ranged approximately from ${\varphi}^{\prime}=2^{\circ}$ to ${\varphi}^{\prime}=7^{\circ}$.