• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.864-870
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• 2018

The effect of lower bed height on the collapse velocity was investigated for a two-stage bubbling fluidizedbed (0.1 m in diameter, 1.2 m high) connected with a standpipe (0.025 m in diameter) for solid transport. Air was used as fluidizing gas and mixture of coarse (< $1000{\mu}m$ in diameter and $3625kg/m^3$ in apparent density) and fine (< $147{\mu}m$ in diameter and $4079kg/m^3$ in apparent density) particles as solid particles. Mixing ratio of fine particles, height of the lower bed and the distributor of the upper bed were considered as experimental variables. The collapse velocity increased with static height of the lower bed. However, the effect decreased as the mixing ratio of fine particles increased. The effect seemed to be attributed to the increase in height of the dense layer of coarse particles that prevented the gas from flowing into the standpipe, not in pressure drop for the standpipe, as the bed height increased. The collapse velocity decreased a little as the pressure drop of the distributor of the upper bed increased. An improved correlation was proposed for predicting the collapse velocity.

• Journal of the Korean Geotechnical Society
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• v.23 no.11
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• pp.77-85
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• 2007

This paper investigates the mechanical characteristics of composite geo-material which was developed to reuse both dredged soils and bottom ash. The composite geo-material used in this experiment consists of dredged soil taken from the construction site of Busan New Port, cement, air foam and bottom ash. Bottom ash is a by-product generated at the Samcheonpo thermal power plant. Several series of laboratory tests were performed to investigate behavior characteristics of composite gee-material, in particular the reinforcing effect by mixing bottom ash. The experimental results of composite geo-material indicated that the stress-strain relationship and the unconfined compressive strength are strongly influenced by mixing conditions. Especially it was observed that the compressive strength of composite geo-material increased with an increase in bottom ash content due to reinforcing effect by the bottom ash. Compressive strength of composite geo-material increased with the increase in curing time. The 28-day strength of composite geo-material is $1.7{\sim}1.8$ times higher than the 7-day strength. The moist unit weight strongly depended on air-foam content as well as bottom ash content added to the composite goo-material. In composite geo-material, secant modulus ($E_{50}$) also increased as its compressive strength increased due to the inclusion of bottom ash.

• Journal of Ocean Engineering and Technology
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• v.20 no.1 s.68
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• pp.7-15
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• 2006

In this research, the behavior characteristics of cement mixing lightweight soil (CMLS) for recycling of dredged soil in the Nakdong River estuary are experimentally investigated. CMLS is composed of the dredged soil from Nakdong River estuary, cement, and air foam. For this purpose, uniaxial compression tests are carried out for artificially prepared specimens of CMLS, with various initial water contents, cement contents, and mixing ratio of dredged soils. The experimental results of CMLS indicated that the compressive strength is strongly influenced by the cement contents, rather than water contents and air foam. Compressive strength of CMLS increased with an increase in cement content, while it decreased with an increase in water content and air foam content. It was also found that the modulus of deformation E50 was in a range of 44 to 128 times greater than the value of uniaxial compressive strength, cured in 28 days.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.853-860
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• 2003

Relationship between axial strain and volumetric strain of Light-Weighted Foam Soil (LWFS) are investigated. LWFS is composed of the dredged soil from offshore, cement and foam to reduce the unit weight and also increase compressive strength. For this purpose. the triaxial compression tests are carried out on the prepared specimens of LWFS with various conditions such as initial water contents, cement contents, and curing stresses, The test results of LWFS Indicated that the axial strain - volumetric strain relationship is almost linearity with increase cement contents and the unit weight but the relationship is non-linearity with decrease cement contents and the unit weight. In this study, it is found that assuming no change of cross section area of LWFS, axial strain occurring the poisson's ratio of zero, that the axial strain same to volumetric strain, steeply increases with decrease the unit weight, initial water content, and cement contents.

• Journal of computational fluids engineering
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• v.16 no.2
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• pp.94-101
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• 2011

The fast pyrolysis characteristics of lignocellulosic biomass are investigated for a bubbling fluidized bed reactor by means of computational fluid dynamics (CFD). To simulate multiphase reacting flows for gases and solids, an Eulerian-Eulerian approach is applied. Attention is paid for the primary and secondary reactions affected by gas-solid flow field. From the result, it is scrutinized that fast pyrolysis reaction is promoted by chaotic bubbling motion of the multiphase flow enhancing the mixing of solid particles. In particular, vortical flow motions around gas bubbles play an important role for solid mixing and consequent fast pyrolysis reaction. Discussion is made for the time-averaged pyrolysis reaction rates together with time-averaged flow quantities which show peculiar characteristics according to local transverse location in a bubbling fluidized bed reactor.

• Journal of the Korean Society of Combustion
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• v.3 no.1
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• pp.41-48
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• 1998

A numerical study on combustion in a fluidized bed is based on three dimensional mixing and dispersion phenomena in the bed owing to the bubble growth in the vertical direction. As fluidizing velocities increase, bubble diameters increase, which activates the fuel dispersion in the bed. The combustion rates, however, reduce due to the decrease of gas exchange rates between bubble and emulsion phases. Fuel distributions in the bed are dependent on fluidizing velocities, equivalence ratios, fuel particle diameters, fuel feeding points, and the number of fuel feeders.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1069-1080
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• 2008

The mechanical characteristic of Lightweight Foamed Soil(LWFS) are investigated in this research. LWFS is composed of the in-suit soil, cement and foam to reduce the unit-weight and increase compressive strength. The unconfined compressive tests are carried out on the prepared specimens of LWFS with various soil types to investigate the relationship between compressive strength of LWFS and physical properties of soil. The result indicate that coefficient of gradation($C_g$) and liquid limit(LL) are more important factor affecting compressive strength than other physical properties of soil and coefficient of gradation($C_g$) and liquid limit(LL) can standard to determine the optical soil among the in-situ soils for LWFS.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.483-490
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• 2002

A massive amount of marine clay produced as dredging of coast and sea bed is often dumped in open sea and filled in pond. The treatment of marine clay demand a large area and make fatal environmental problems for echo system. This research work intend to manufacture a light-weight landfill materials which are produced by mixing the dredged marine clay with various amount cement and foam. An extensive Uniaxial and Triaxial compression test are carried out to investigate the strength characteristics of the light-weight cement mixed marine clay with foam under various test conditions. The results indicated that the required unit weight has been achieved with negligible change after 28days curing time in water. It is also recognized that the compressive strength of light-weight landfill materials linearly decrease with increasing initial water content, and the rate of strength decrease with increasing initial water content in water curing was smaller than that of air curing Futhermore, the rate of strength decreased with increasing initial water content, however, the rate become smaller as cement content increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.40-41
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• 2013

The energy consumption by buildings approximately reaches 25% of total korea energy consumption. The greatest part in the buildings of the energy consumption is building facade. but a few research projects on concrete compising more than 70% of outsider of buildings has been tried. This research is structural insulation concrete what improved insulation performance using micro form admixture and calcined diatomite powedr and lightweight aggregate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.9
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• pp.837-845
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• 2013

An airlift pump can be used to pump liquids and sediments within itself, which cannot easily be pumped up by a conventional method, by using the airlift effect. This characteristic of the airlift pump can be exploited in a DCFC (Direct Carbon Fuel Cell) so that molten fuel with high temperature may be carried or transported. The basic characteristics of airlift are investigated. A simple system is constructed, where the reservoir is filled with water, a tube is inserted, and air is supplied from the bottom of the tube. Then, water is lifted and its flow rate is measured. Bubble patterns in the tube are observed in a range of air flow rates with the parameters of the tube diameter and submergence ratio, leading to four distinct regimes. The pumping performance is predicted, and the correlation between the supplied gas flow rate and the induced flow rate of water is found.