• Journal of the Korean Geosynthetics Society
• /
• v.19 no.1
• /
• pp.103-110
• /
• 2020

The DMM (Deep mixing method) is a construction method in which an improved pile is installed in the soft ground by excavation ground using an auger and then mixing ground stabilizer with soil. Improved pile installed in the soft ground by the DMM may have different compressive strength depending on the properties and characteristics of the soil. In the previous study, laboratory tests were performed on the ground stabilizer for the DMM developed by using the ash of the circulating fluidized bed boiler as a stimulator for alkali activation of the blast furnace slag. And the test results were analyzed to derive the correlation between the unit weight of binder (γ_B) and the uniaxial compressive strength (q_u). In this study, comparative reviews were conducted on the correlations derived from the same laboratory tests on soil material collected from the Saemangeum area and the stability of the site was evaluated by analyzing the test results performed at the site. As a result, the clay collected from the Saemangeum area satisfies the correlation between the unit weight of binder (γ_B) and the uniaxial compressive strength (q_u) derived from the previous study. And the result of the test at the field showed a higher uniaxial compressive strength than the standard strength at the field, indicating excellent stability.

• Journal of the Korean Geotechnical Society
• /
• v.28 no.6
• /
• pp.71-79
• /
• 2012

Sand compaction pile and stone column replacement methods have been commonly used for improving soft ground in the nearshore. Recently, DCM (Deep cement mixing) method, which can harden soft clays by mixing with cement, is more popularly used in such soft ground improvement. Sandy soils also exist in the seashore. Therefore, in this study, the effect of salinity in sea water and curing methods on the strength of cemented sand was evaluated in terms of unconfined compressive strength (UCS). The sand was mixed with five different cement ratios and distilled water or sea water, and then compacted into a cylindrical specimen. They were cured for 3 days under sea water for DCM construction condition and air cured for onshore curing condition. When a specimen was cured under sea water without confinement, it was easily collapsed due to initiation of cracks. When the cement ratio and curing method were the same, the UCS of the specimen without sea water was at maximum 3.5 times higher than those with sea water. The sea water used for mixing sand had more influence on strength reduction than the sea water used for curing. When the cement ratio was the same, the UCS of air-cured specimen was at average 2 times higher than those of water-cured specimen, regardless of water used.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.2 s.69
• /
• pp.247-255
• /
• 2004

An experimental program was undertaken to develop seismic retrofit methods of existing steel moment connections with floor slab for improved seismic performance. Five full-scale composite specimens were tested under cyclic loading. Conventional through-diaphragm connections [please check this; no search results were found for through-diaphragm connections] composed of square-tube column and H-beam were retrofitted by adding either a bottom-flange dogbone (RBS) or an improved welded horizontal stiffener at the beam bottom flange. The effectiveness of the proposed retrofit connections schemes was evaluated. The specimen retrofitted using the RBS concept at the bottom flange showed poor connection ductility. In contrast. specimens with the proposed horizontal stiffener details exhibited improved connection ductility.

• Korean Journal of Soil Science and Fertilizer
• /
• v.41 no.6
• /
• pp.379-386
• /
• 2008

Calcined clay granules (pellet) have been used as a soil conditioner. The space among the pellets can secure drainage of water in soil and, simultaneously, can keep water for plants in the inner pore of that. However, the usage of the pellet has been restrained because fabrication of that requires a high energy and cost for heating over the temperate of $1000^{\circ}C$. Recently, SCS(Self-propagating Combustion and Sintering) method was developed and this method use the combustion energy of the preliminary mixed combustible. The SCS method is suitable to fabrication of small porous aggregate and requires a very low cost. This research applied the SCS method to coal refuses for fabrication of soil conditioner pellets. The coal refuses were pulverized under the size of $100{\mu}m$ and the pulverized powders were pelletized to the size of 4~6mm. The pellets were heated at the temperature of $1200^{\circ}C$ in the SCS furnace that was specially prepared for this research. Characteristics of the pellets were investigated and were compared with that of ordinary calcined clay pellet of kaolin; porosity, pore size distribution, bulk density, pH and etc.. Characteristics of the moisture retention in the pellets were measured by the centrifugal method: ASTM D425-88. The pellets of the coal refuses showed the higher values of the field capacity and the plant-available water than that of kaolin pellet. These results suggest the very low cost process that can utilize the coal refuses and can fabricate the lightweight porous soil conditioner of the very high plant-available water.

• Aerospace Engineering and Technology
• /
• v.3 no.2
• /
• pp.208-216
• /
• 2004

Advanced overload protection module for full scale airframe structural test was developed by improving the existing overload protection module. When performing the full scale airframe structural test, overload can be applied to the test article due to unexpected situations such as system shutdown, test article failure, and deficiency of design strength. Therefore, the overload protection module is needed for protecting the test article in unexpected overload situations. In this paper, the function of the existing overload protection module was summarized for each component and the problems encountered when using it in structural test were analyzed in addition, the development of advanced overload protection module was described.

• Microbiology and Biotechnology Letters
• /
• v.16 no.3
• /
• pp.182-186
• /
• 1988

The possibility of strain improvement of cellulolytic fungus, Penicillium verruculosum via protoplast fusion was investigated. The cellulolytic activities of the six fusants, finally selected for their hyper-cellulolytics were 2 times of those of wild type and 1.2 to 4.4 times of those parental auxotrophs. It was confirmed that the nuclear fusion occurred in fusants by their DNA contents and nuclear staining with Giemsa. It was also found that the fusants were aneuploids, and their genetic stability was demonstrated from the subculture for four months.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.2
• /
• pp.73-80
• /
• 2015

It had been almost a half century since Apollo Mission was ended. However, in these days, a lot of researches are being conducted for restoration and making improvements in technologies used in Saturn V rocket's development. This study reviews the first stage of Saturn V rocket(S-IC), from development history to technologies in various subsystems such as engine purge system, POGO suppression system, hydraulic and pneumatic control system, propellant dispersion system, telemetry system and retrorocket system. Understandings of S-IC stage's operation systems would be helpful in understanding of launch vehicle system and reduction of time and cost in future development process.

• Proceedings of the Korean Information Science Society Conference
• /
• 2007.06c
• /
• pp.436-439
• /
• 2007

Noise reduction in the image is very important to improve the quality of the image. This paper discusses a new noise reduction technique which uses the On/Off spatio-temporal structure of the receptive fields. Also this paper proposes a structurally improved artificial vision system which incorporates the sphere type retina structure, an improved On/Off spatio-temporal receptive fields structure, and chiasm for hemianopia testing.

• Korean Journal of Soil Science and Fertilizer
• /
• v.12 no.2
• /
• pp.83-89
• /
• 1979

To improve the physico-chemical properties of sandy alluvial soils for paddy rice, several soil amendments such as wollastonite, dolomite adding red earth and compost were applied compositely. The results are summarized as follows. 1. The application of soil amendments caused an increase of calcium, magnesium and silica contents in the soils, and it was also possible to maintain a high pH during the cropping season. 2. Among the mineral elements in the plant, calcium and silica content were increased by the treatment of adding red earth, dolomite and wollastonite. 3. By the application of wallastonite and dolomite, the phosphorous content in the plant decreased in comparison with no-amendment treatment, and the potash in the plant also decreased after the ear formation stage of the rice. 4. The most desirable treatment (adding red earth+dolomite+extra N) resulted in 19% increase of rice yield, while the composite of wollastonite and compost brought 10% yield increase. The high ripeding ratio was the factor which influenced the yield favorably.

• Korean Journal of Food Science and Technology
• /
• v.42 no.2
• /
• pp.125-129
• /
• 2010

Isoflavone distribution and $\beta$-glucosidase activity in 16 commercially available doenjang samples were determined. Twelve of the samples were home-made doenjang (HMD) with a relatively long fermentation period and 4 of the samples were factory-produced doenjang (FPD) from four different manufactures. Total isoflavones (TI) in the HMD ranged from $370-723\;{\mu}g/g$, while those in FPD ranged from $179-537\;{\mu}g/g$. The isoflavone distribution in HMD was different from those in FPD. Generally, the TI in HMD was higher than those in FPD. The major isoflavone was aglycones, which ranged from 42.98 to 89.96% in HMD and from 35.51 to 93.48% in FPD. Isoflavones in the $\beta$-glucoside forms were not detected in tested FPD samples. Principal components analysis (PCA) of the isoflavone profiles showed that HMD were differentiated from FPD. First principal component (PC1) and second principal component (PC2) expressed 43.6 and 22.9% of the data variability, respectively. $\beta$-Glucosidase activity in doenjang was lower than that in raw soybeans. The results of this study can be used to understand the differences in the isoflavone distribution in traditionally manufactured and factory produced doenjang.