• Weed & Turfgrass Science
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• v.2 no.1
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• pp.82-87
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• 2013

This research will be utilized as a base line data by researching on growth and the accumulation of inorganic nutrients during the cultivation period of zoysiagrass and also to establish a cultivation strategy of zoysiagrass. It involves the management such as fertilizer and mowing which ultimately led to the difference of growth and accumulation of inorganic nutrients. The accumulation of inorganic nutrients after mowing, the amount of accumulation was small when compared to the amount lost for the shoot, rhizome and root. Difference in the accumulation of inorganic nutrients, but as for K, Ca and Mg accumulation it shows similar aspects to N accumulation. The orders of inorganic nutrients in zoysiagrass were N > K > P > Ca > Mg. The characteristics of inorganic nutrients absorption of such zoysiagrass acts as the foundation of cultivation, and in the aspect of making decisions on the fertilization amount and soil management, it is closely related to the requirement on nutrients. In order to increase the productivity based on the zoysiagrass's growth and density rate improvement, accumulation of inorganic nutrients per growth period needs to be analyzed, and supplying nutrients in an efficient method suitable to the growth period is advisable, so such basic research was necessary.

• Weed & Turfgrass Science
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• v.2 no.1
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• pp.95-99
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• 2013

To investigate the actual condition of production and management of sod, a questionnaire was ask to 57 farmers in major cultivated areas of turf sod in Korea in 2010 and 2011. The results of the turfgrass management situation analysis showed a mixed farming where the ratio of the principal work and the side work progress similarly, and for the landholding type depending on the management scale, the rental ratio was high for a scale over 0.5 ha. Sod production farmers has high-profile in new varieties of turfgrass, integrated management of the fertilization and soil or disease and insect pest however the future of the turfgrass industry does not seem optimistic due to the problems such as market stability or scarcity of worker. Obtaining of information on culture methods depended neighbor's experience (81.8%). Concerning the varieties preference analysis, the 32.1% of farmer answered that the reproductive rate was a key factor for the new variety. Sod production farmers want to receive financial support (28.1%), improvement of distribution structure of sod (26.6%), and spread of good variety turfgrass (23.4%).

• Journal of the Korean Geotechnical Society
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• v.30 no.2
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• pp.65-76
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• 2014

For soil improvement, sand mats or sand compaction piles are often constructed on soft marine clays. In such cases, some amounts of sand and clay are inevitably mixed. Sand or gravel often exists in the weathered soils near the slope surface. This research investigates the effect of mixing sand content on consistency limits and shear strength of clays. Firstly, sand was mixed with kaolinite or bentonite at 0, 9, 17, 23, 29, 33, 50% and then liquid and plastic limits were measured. Both plastic and liquid limits decreased as a sand content increased. The water content of clay-sand mixtures with different sand content increased by 10% or 20% step by step and then their undrained shear strength was measured using a portable vane shear device called Torvane. For all cases, undrained shear strength of clay-sand mixtures decreased rapidly until reaching a certain value. Their state changed from undrained to drained state gradually as the sand content increased, which caused their undrained shear strength to decrease. On the other hand, a series of direct shear tests were also conducted on such clay-sand mixtures to investigate the effect of sand content on cohesion and angle of internal friction. It was found from clay-sand mixtures that their cohesion decreased but angle of internal friction increased as the sand content increased.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.7
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• pp.518-524
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• 2013

A pilot-scale test-bed was operated employing three soils with different grain sizes dredged from the Nakdong River to obtain the design and operation parameters of the multi-purpose filtration pond, such as the filtrate productivity of the filter sand, the appropriate removal period of the surface clogging and the contaminant removal efficiency. The cross-flow velocities were applied stepwise ranging from 0 to 40 cm/sec in order to simulate the various velocities in the artificial stream of the pond. Results showed that a filtrate production rate of 5~3 $m^3/m^2-day$ was maintained by removing the surface clogging every 7 to 13 days and that the filtrate quality was not affected by the factors of the filtrate production rate, the grain size of the filter sand and the cross-flow velocity. Results also showed that most of the removal occurred within 50 cm of the top soil and that the removal efficiencies with the filtration distance of 2.4 m were 80~95% for turbidity, 20~30% for COD, 75~90% for BOD, 5~20% for total nitrogen and 20~60% for total phosphorus, which suggested that particulate matters had a high removal efficiency.

• Korean Journal of Environment and Ecology
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• v.28 no.1
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• pp.24-32
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• 2014

Our study is purposed to understand effect on spatio-temporal variability of macroinvertebrate community 11 sampling times at 4 sites between two streams (Shinchon stream and Gongji stream in Chuncheun City) from May 2011 to October 2013. In this study, the possible physical factors on spatio-temporal variability of macroinvertebrate community were discussed. After stream improvement project, the effects of anthropogenic disturbance in study sites appeared as increased water temperature more than $30^{\circ}C$ and the difference of water temperature between Shinchon stream and Gongji stream was by maximum $9^{\circ}C$ on 2012. The monsoon rainfall decreased number of species, individuals and biodiversity index of macroinvertebrate community, particularly, in Shincheon stream compare to Gongji stream. Dominant species of macroinvertebrate taxa was caddisfly in Shincheon stream and Diptera in Gongji stream but on August 2013, it was dominated by Diptera, Chironomidae spp. in all study sites. The spatio-temporal variability of macroinvertebrate community in the streams may be useful as bio-indicator influencing anthropogenic factors such as soil erosion (landslide or cultivation) or monsoon rainfall.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.6
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• pp.1063-1076
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• 2017

To improve the productivity of the earthwork, a fleet management system for construction equipment was suggested in previous studies. But there were some gaps between theory and practice. To overcome this problem, some opinions are gathered form experts and field engineers and four improvements have been proposed and reflected in the system. First, the previous system consists of one hardware module, so it is hard to install it at a control office and construction equipment at the same time. The server module for the office and the mobile module for construction equipment are separately developed. Second, the transportation algorithm that is used in the previous system can generate shortest paths for the earthwork distribution, but embankment areas are not gathered. This situation leads to a decrease in compaction productivity. A modified algorithm for earthwork distribution is suggested. Third, the automated coordinate transformation is performed to show the position of construction equipment on the 3D terrain in real-time. Fourth, construction equipment groups should be formed in the initial stage of earthwork and the number of equipment of each groups should be changed by operation status and site environment. But this functions did not work properly in the previous system. This problem is corrected in the proposed system. The improvements can make the proposed system much more realistic one and can leads to an increase in the productivity of earthwork operations.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.7 no.1
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• pp.85-92
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• 1969

The goal for the improvement of rice culture in our country is to increase the rice yield per unit area, and that thoroughly, to equalize the rice yield per unit are highly by adaptation of high technique, while on the side of the efficiency, to increase the productivity of the labour through the cooperative work. And then, the theory for execution of the cooperative rice culture which is the productive system embodying the goal above and the expected effects as well as the future prospect for the development of the cooperative rice culture must be studied and defined. The results studied up to now are summarized as follows: 1. The cooperative rice culture is one of the most effective ways to execute highly efficient farm management and to supply the technical details on the cultivation for equalized high yield per unit area in the rice cultivating districts. 2. For the most effective accomplishment of the cooperative rice culture, the water control, and soil and variety of rice must be investigated in advance an then the basic technical details for the rice culture must be defined. 3. The rice cultivation calender is drawn up with the main technical details of rice culture by the mutual agreement of all farmers belong to the cooperative farm. All technical details for the rice cultivation in the cooperative farm are standardized by the rice cultivation calendar and the main technical operations should be worked together and the other operations executed individually. 4. The technique for rice cultivation, which was difficult to be introduced in the individual farm management, could be introduced easily to the cooperative rice culture, and the rice yield of the cooperative farm was increased 23.3% compared to that of common farm in 1968. 5. At present, the type of the cooperative rice culture is a primary type of the agreement for farm management, rarely including the associated operation type and the contracted operation type for a part of operation, However, for stabilized high yield through the mechanization of the cultivation system, the cooperative farm must be developed for a course promoting the associated operation type including the technique trust type and the contracted operation type according to the condition of location.

• The Korean Journal of Quaternary Research
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• v.18 no.2 s.23
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• pp.107-107
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• 2004

In this paper we have introduced some results of study on stand growth pattern and stand structure of larch forest which are located in selected forest sites of Khangai and Gobi-Altai mountain ranges of Mongolia. Our investigations showed that growth intensity and stand structure in western Mongolia are very specific from the other forest vegetation zones of Mongolia. Studies on the stand structure and growth trend indicate that tree types of stand structure and different types of growth of Larix sibrica are very common in Western Mongolia. These peculiarities of stand structure and growth of larch stands in Western Monolia could be used for inventory work and an improvement of the forest management in Western Mongolian region. The larch tree is the dominant tree species in Western Mogolia. Forest cover of the region is about 15%, which is two times higher than the country's average. In this region forest area is divided into 4 forest sub-regions: the Central Khangai, Western Khangai, North Eastern Khangai and South Easterun Khangai sub-regions including taiga, pseudo taiga, sub taiga, sub-alpine and forest steppe belts. Silviculture practices and forest research management request to study forest growth trends in local and general conditions, which means to indicate a change of taxonomic characteristics of stand from time to time including diameter, height, basal area, growth stock etc. The forest management practice mostly uses tables of forest growth and yield based on the results of long term research on forest growth. Forest yield tables and other relevant forest standards of Russia are used for the forest inventory and forest management. They are not able to determine forest structure and growth peculiatities of Mongolian forests. Studies on forest resource assessment in Mongolia indicate that after logging operations and forest fires the natural regeneration of desired species such as pine and larch often does not succeed. This situation forces to take a different approach of forest management and silviculture practice depending on the stand structure and growth rate of the forest stands. According to our investigation in last years, forest growth pattern of larch forest depends mostly on stand structure, stand age and growth condition including forest soil, climate and location in different slopes. Due to improve environmental function of forest ecosystem in the region, it is needed to conduct very comprehensive study of high mountain forest ecosystem in selected sub-regions.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.127-137
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• 2018

Gravel Compaction Pile (hereinafter referred to as GCP) is a ground improvement technique by packing crushed stones on fragile clay ground, pressing it, and forming stakes on the foundation. Although many researchers have analyzed stress behavior of GCP composite ground on domestic GCP technique using laboratory experiment and field experiment, analyses of stress behavior according to the difference of stiffness of mat foundation loaded on the upper foundation of GCP composite ground have not been done actively. Therefore, this study aimed to identify the stress concentration ratio in accordance with the difference of basis stiffness by interpreting figures. To perform this, replacement ratio was changed and modelled using ABAQUS, software for finite element analysis and analyzed the stress concentration ratio, amounts of settlement, and maximum amounts of horizontal displacement of composite ground in accordance with the difference of stiffness. An analysis showed that the stress concentration ratio of rigid foundation was highly assessed than unloading of flexible foundation in case of unloading, while amounts of settlement under flexible unloading condition were slightly higher than under rigid condition. This indicates that the characteristic of stress behavior on the different stiffness of upper foundation needs to be clarified. In addition, the maximum horizontal displacement was generated in a constant level regardless of the difference of stiffness.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.509-529
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• 2019

This study performs to evaluate the role of filter material at alluvial well for intake of riverbank filtration and the applicability and improvement effect of dual filter well. To achieve this objective, dual filter intake well and single filter intake well were installed with different filter conditions at riverbank free surface aquifer in soil layer then we evaluated filter material condition, permeability, optimum yield and well efficiency according to yield in drawdown test. As a results, we assumed forming dual filter layer minimizes sudden speed changes at boundary between aquifer and filter layer by cushioning of groundwater flow. This suppresses warm current then intake groundwater efficiently, therefore it seems decreasing peripheral groundwater level changes in spite of higher intake water amount than single filter intake well. Furthermore, we confirmed by test, installing dual filter improves permeability, optimum yield and well efficiency. The result will be used by combining with former study to set up standard of design/construction of dual filter intake well at alluvial aquifer layer. Furthermore, we expect this result will be used to prove application effect of dual filter intake well compared to single filter one and radial collector well which are mainly applied on riverbank filtration.