• Journal of Bio-Environment Control
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• v.2 no.1
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• pp.1-8
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• 1993

Experimental and theoretical analyses were carried out to investigate the heat exchange characteristics of the nutrient solution cooling system utilizing ground water. The material of heat exchanger used in the experiment was polyethylene and the cross-flow type was adapted in which nutrient solution was mixed and ground water unmixed. For the exchanger surface area of 0.33$m^2$ and flow rates of ground water of 1-6$\ell$/min, NTU(number of transfer units) and effectiveness of experimental heat exchanger were 0.1-0.45 and 10-35％, respectively. Therefore these results showed that the hydroponic greenhouse of 1,000$m^2$(300 pyong) with the ground water of 10$m^2$/day could cover about 55-70％ of maximum cooling load in summer.

• Journal of the Korean Geotechnical Society
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• v.30 no.1
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• pp.27-36
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• 2014

In this study, laboratory test was carried out on uniaxial compressive strength by making 320 specimens in total, which were divided into two groups considering the curing time of 7 and 28 days for 80 cases mixed with stabilizers of 8%, 10%, 12%, 14% of 20 cases of clayey, sandy, and gravel mixed ground conditions to understand laboratory strength characteristics of deep mixing specimen for field application in various ground conditions. As a laboratory result, all specimen showed a clear tendency to have uniaxial compressive strength increase as the curing time and the stabilizer mixing ratio increased, and the strength increments depending on the age by ground types were, around 40.0% for clayey and gravel mixed grounds, 48.4% for sandy grounds which was the highest, and for the increment of stabilizers, around 37.0% for grounds with mixing ratio less then 14%, and 49.6% when the ratio was 14% which was the highest. Also, with sandy grounds, it showed a tendency to have a constant amount of strength increment as the stabilizer mixing ratio increased, for clayey mixed grounds, the strength increment tendency seemed to be similar to gravel mixed grounds. Due to these tendencies, it is concluded that we are able to propose a stabilizer mixing ratio for various ground conditions.

• Tunnel and Underground Space
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• v.29 no.6
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• pp.394-406
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• 2019

Difficult ground conditions (e.g., fault zone and mixed grounds) are highly probable to appear in subsea and urban tunnels because of the shallow working depth and alluvial characteristics. TBM usually experienced decrease of penetration rate and increase of downtime when it meets these difficult ground conditions. The problems are usually caused by the adverse geological conditions, and it is preferable to determine the optimal operational parameters of TBM based on the previous operational data obtained while excavating a preceding tunnel. This study carried out for efficient TBM excavation in fault zone and mixed grounds. TBM excavation data from the tunnel site in Singapore and the characteristics of the TBM excavation data was analyzed. The key operational parameters (i.e., thrust, torque, and RPM), penetration rate, and downtime were highly influenced by the presence of fault zones and mixed grounds, and the features was discussed. It is expected that the results and main discussions will be useful information for future tunneling projects in similar geological conditions.

• Land and Housing Review
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• v.8 no.1
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• pp.13-22
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• 2017

In this study, triggering mechanism of ground sinking was analyzed through groundwater flow analysis on the basis of a case of the ground sinking occurred in Yongsan in 2015. The results of geotechnical investigation performed before and after the ground sinking were analyzed for the accurate understanding of geological features in the study area. The numerical groundwater flow analysis was performed to evaluate the influence of the flow behavior from the surrounding area toward the excavated site using software of Visual MODFLOW. As a result, it was found from the geotechnical analysis that the strata of sedimentary layer along the sunken area in the vertical direction was mixed significantly after the ground sinking compared with the status of the soil condition before the ground sinking. Piping was occurred at the toe of cut-off wall in the sandy gravel layer, and this phenomenon was predicted by the numerical flow analysis. Sequential ground displacement scenario of the ground sinking was derived from the geotechnical in situ test and numerical flow analysis performed in this study.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.1
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• pp.86-92
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• 2012

When missile is launched, a launcher needs to be leveled with accuracy to avoid the systems's instability. In general, a launcher is leveled by adjusting the stroke of leveling jacks; however, it is still challenge to control the leveling jacks fast and accurately. This paper thus proposed an innovative algorithm for compensating ground inclination of a missile launcher to expand operational field of a missile launcher. Using two inclinometers attached on a launcher, a base jack for leveling is selected and the mixed gradient where launcher stands on can be estimated. Due to the limited stroke, the launcher can compensate its ground inclination within maximum stroke margin. Then, the ground inclination of a launcher can be compensated by calculated angle using weighting factors. The effectiveness of proposed algorithm is proved with a prototype missile launcher.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.313-318
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• 2001

The cost of producing ready mixed concrete(remicon) has increased due to the rising cost of raw materials for concrete and transportation caused by the upturn of oil price. In contrast, its orders have also decreased due to the recession of the construction industry. In addition, the cost of delivery has decreased owing to the excessive competition among manufacturing companies, so manufacturing companies began mixing ground granulated blast-furnace slag or fly ash to lower the cost. However, there is no way to determine whether the strength of the concrete using the admixture is satisfied or dissatisfied with design strength at the early age. The purpose of this study is dedicated to early strength estimation of concrete mixed with an admixture, ground granulated blast-furnace slag.

• The Korean Journal of Ecology
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• v.22 no.2
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• pp.65-68
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• 1999

In December-January of 1996-1997 and 1997-1998, information was gathered about vertical distribution of foraging sites of tits in 34 flocks in coniferous and deciduous forests. There was a significant effect of forest type on the distribution of foraging sites of each species. Habitat was classified into 5 height layers vertically: ground, bushes (usually＜1.5 m, up to 3 m), tree layer 1 (up to 1/3 of tree height), tree layer 2 (1/3-2/3 tree height). and tree layer 3 (＞2/3 tree height). There were differences among species: great tit (Parus major) foraged mostly on the ground, coal tit (P. ater) and long-tailed tit (Acrocephalus caudatus) - on the highest tree layer, marsh tit (P. palustris) was often seen on bushes, and varied tit (P. varius) - in tree layer 2. Smaller species used upper and outer parts of trees. suggesting that, like in most other similar studies. larger dominant species prevented smaller species from using inner parts of trees.

• Journal of the Korean Geotechnical Society
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• v.16 no.2
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• pp.79-89
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• 2000

The application of stabilization method has increased because of short construction periods, no environmental problems with dumped and replaced soil, assurance of required strength and economical effect with mid to small size construction. The unconfined and triaxial(UU-condition) compression tests were executed with each mixing sample for the study of the improvement effects and the effect of design-parameters by the stabilization methods. Three typical stabilizers, which are representative in Korea, were applied in this study, and three common soils(very soft clay, general weathered soil, common clay), which are common in Korea, were used in this study. In this study, the effect of engineering factors(soils, stabilizers and water contents, etc.) which are important parameters for the improvement effects of mixed ground by stabilizers, was analyzed. As results, the tendencies of design-parameters(unconfined compression strength, deformation modulus and strength parameter) are presented and the criteria of the application of stabilization methods are suggested.

• Journal of Environmental Science International
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• v.14 no.8
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• pp.719-722
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• 2005

This study is to find the effective way to green perpendicular wall spaces as soon as possible and to get basic data for activating the perpendicular greening on high story building through the experiment of container-type planting ground in which lightened artificial soil mixed with rock wool was put. Comparative studies of the sizes of containers and soil were carried out but separate management was not performed. Four plants(Euonymus fortunei var. radicans, Lonicera japonica, Parthenocissus quinquefolia, Parthenocissus tricuspidata) which have the capability to cover and screen perpendicular spaces were used in the experiment. In result, a container must be equipped with over 15cm depth soil mixed with less than $30\%$ of rock wool.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.06a
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• pp.103-117
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• 2002

During the installation of drilled shafts in very soft ground, to keep the pile shape and to central concrete quality, casing method (wrinkled pipe and embedded steel pipe) and non-casing method have been used. In the construction cost, non-casing method was the most economical. When the wrinkled pipe and the embedded steel pipe casing method are used, an increase of 133% and 123% in the construction cost could be seen. When concrete for drilled shaft was placed under groundwater, underwater unseparation concrete would be used to restrain the concretes's material separation and to control the concrete quality. On the condition of required unseparable and (lowing property was assured, use of less amount of mixed material and flowing material must be recommended.