• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.204-211
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• 2002

Today\`s industrialized plants are required to reduce SOx emitted from stacks at factories, utility power stations, etc. For this purpose, flue gas desulfurization(FGD) system is installed in thermal power plant and gas-gas heater(GGH) is used to play a vital role to reheat the wet treated gas from FGD. The sector plates are located at cold and hot sides of gas-gas heater. They serve as sealing to prevent mixing treated and untreated gases. Therefore, the deformation of the sector plate due to its dead weight and gas pressure should be considered as major factor for the sector plate design. And finite element analysis(FEA) for rotor part in GGH is performed with original model and two weight-reduced models with different diaphragm thickness, respectively. Stress concentrations at rotor diaphragm happen due to the dead weight, pressure difference between treated and untreated gas, and thermal distribution in the rotor. As the thickness of diaphragm is decreased, the stress level is increased. The direction of treated gas and untreated gas flow may affect the stress level.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.6
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• pp.127-134
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• 2001

In order to expand agricultural lands in the western and southern coasts of Korean Peninsula, coarse soils excavated from hillsides have been used as fill materials for reclamation. In order to tackle with the problems and to confirm availability, research on soil improvement involve mixing cement to the fine wet soils. Required undrained shear strength$(C_u)$ for fill material was analysed to be 0.34~1.2 $kgf/cm^2$. It has been known that when cement is added to high water content marine clay its unconfined compression strength increased to 2 $kgf/cm^2$. Consolidation results show that pre-consolidation pressure increased to 1.8 $kgf/cm^2$and 3.4 $kgf/cm^2$ with the addition of 3% and 5% of cement respectively. This result shows that low-height embankments could be constructed without significant compression. Since the effectiveness of improvement may be different site by site, the mix design for each site is necessary in order to optimize it. The process is first to determine aimed shear strength and then optimum mix ratio of cement after carrying out a series of tests.

• Journal of the Korean Ceramic Society
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• v.29 no.10
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• pp.822-826
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• 1992

SiO2 doped sapphire single crystals were grown by Verneuil method using feed material which prepared by adding SiO2 in Al2O3. Crystal growing were attempted with varing doping amount of SiO2 from 0.01 to 1.0 wt% and when the doping amount of SiO2 were 0.01~0.04 wt%, single crystals could be attained. Starting materials for feed powder were 99.99% purity alumina and extra pure SiO2 powder. Mixing these two materials by wet milling for 24 hours and drying the mixture and then was calcined at 900~110$0^{\circ}C$ for 2~4 hours. The grown crystals had yellowish color and were somewhat transparent. During growing process the flow range of oxygen was 5~7.5ι/min and of hydrogen was 13~25ι/min, the average growth rate was 7.0~11 mm/hr. The pressure of gases were fixed at 5psi. The color of crystal was appeared and mechanical property of sapphire was developed by doping of SiO2.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.665-672
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• 2002

In order to expand agricultural lands in the western and southern coasts of Korean Peninsula, coarse soils excavated from hillsides have been used as fill materials for reclamation. In order to tackle with the problems and to confirm availability, research on soil improvement involve mixing cement to the fine wet soils. Required undrained shear strength(c$\sub$u/) for fill material was analyzed to be 0.34∼1.2kg/$\textrm{cm}^2$. It has been known that when cement is added to high water content marine clay, its unconfined compression strength increased to 2kg/$\textrm{cm}^2$. Consolidation results show that pre-consolidation pressure increased to 1.8kg/$\textrm{cm}^2$ and 3.4kg/$\textrm{cm}^2$ with the addition of 3% and 5% of cement respectively. This result shows that low-height embankments could be constructed without significant compression. Since the effectiveness of improvement may be different site by site, the mix design for each site is necessary in order to optimize it. The process is first to determine aimed shear strength and then optimum mix ratio of cement after carrying out a series of tests.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.407-426
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• 2008

The bentonite slurry has been used as the stabilize suspension for wet process bored pile construction in Thailand. The bentonite suspension has benefit on filtration in the sand layer, but it creates thick cake film along pile shaft and loose sedimentation at pile toe. The base grouting technique was widely used to rectify the soft base or loose sedimentation problem of bored pile. The base grouting technique was not increased only end bearing capacity, but was also more increase in skin friction capacity of the bored piles. The comprehensive researches on base grouting was carried out by installing PVC casing inside the shaft to allow the drilling through the pile base in order to collect the soil sample below the pile tip. The polymer based slurry recently was used to replace the bentonite slurry to overcome the thick cake film along pile shaft as well as loose sedimentation at pile toe. The extent research on polymer slurry by physical model was performed to verify the real behavior of polymer. The appropriate mixing ratio of polymer was proposed. The design skin friction coefficient, $\beta$ and end bearing coefficient, Nq, for sand layer base on fully instrumented tested pile were proposed. The application on remedial of the lose capacity bored pile with large displacement in Bangladesh was proposed and discussed.

• Corrosion Science and Technology
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• v.19 no.1
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• pp.31-36
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• 2020

An efficient wet process approach to modifying natural graphite (NG) electrodes for Li-ion batteries is introduced in this paper. With homogeneous mixing and thermal decomposition of NG with diammonium phosphate ((NH₄)₂HPO₄), phosphorus and nitrogen were successfully incorporated into the surface layer of NG particles. Electron microscopy and X-ray photoelectron spectroscopy analyses demonstrated that the surface was well modified by this process. As a result, the treated NG electrodes exhibited much improved electrochemical performance over pristine NG at two different temperatures: 25 ℃ and 50 ℃. Excellent capacity retention of 95.6% was obtained after 100 cycles at 50 ℃. These enhanced properties were confirmed in a morphology analysis on the cross-sections of the NG electrodes after galvanostatic cycling. The improved cycle and thermal stabilities can be attributed to the surface treatment with phosphorus and nitrogen; the treatment formed a stable solid electrolyte interphase layer that performed well when undergoing Li insertion and extraction cycling.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.439-444
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• 2010

The usual ceramic process of mixing and milling in state of oxide of $ZrO_2$ and $CeO_2$ was adopted in wet process to manufacture Ce-TZP in this study. The maximum dispersion point of every slurry manufactured with mixture of $ZrO_2$ and $CeO_2$ was neat at pH10. The stable slurry in average particle size of 90 nm can be manufactured when it is dispersed with use of ammonia water and polycarboxylic acid ammonium. The sintered Ce-TZP ceramics manufactured with addition of $CeO_2$ less than 10 mol% was progressed to the fracture of specimen due to the monoclinic phase existence more than 30% at the room temperature. More than 99% of tetragonal phase was created for the sintered body with addition of $CeO_2$ beyond 18 mol%, but the mechanical property degrade on the entire specimen was brought due to the $CeO_2$ existing above 3%. Consequently, the optimal Ce-TZP combined in oxide state was identified in 16 mol% of $CeO_2$ contents.

• KSBB Journal
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• v.8 no.3
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• pp.237-242
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• 1993

Chitin-based fibers have low mechanical strength and hence cannot be used as surgery fiber due to fast degradation In tissues. A new fiber Chitulose was made by mixing chitin with cellulose, both of which have similar structure. A mixture of dimethylacetamide (DMAc) and 6% lithium chloride (LiCl) was found to be an effective solvent system for dissolvoing chitin and cellulose. The Chitulose fiber made by wet spinning of a mixture of chitin and cellulose resulted in the highest degree of strength and flexibility when the ratio of chitin to cellulose was 1.5; 0.2. The fiber maintained mechanical structure even after autoclaving, indicating thermal stability. A biodegradability test of the Chitulose fiber by imbeding in a rat showed that degradation was initiated in 14 days and completely done in 40 days.

• Geomechanics and Engineering
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• v.21 no.4
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• pp.337-348
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• 2020

Tropical organic soils having more than 65% of organic matters are named "peat". This soil type is extremely soft, unconsolidated, and possesses low shear strength and stiffness. Different conventional and industrial binders (e.g., lime or Portland cement) are used widely for stabilisation of organic soils. However, due to many factors affecting the behaviour of these soils (e.g., high moisture content, fewer mineral particles, and acidic media), the efficiency of the conventional binders is low and/or cost-intensive. This research investigates the impact of different constituents of cement-sodium silicate grout system on the compressibility behaviour of organic soil, including settlement and void ratio. A microstructure analysis is also carried out on treated organic soil using Scanning Electron Micrographs (SEM), Energy Dispersive X-ray spectrometer (EDX), and X-ray Diffraction (XRD). The results indicate that the settlement and void ratio of treated organic soils decrease gradually with the increase of cement and kaolinite contents, as well as sodium silicate until an optimum value of 2.5% of the wet soil weight. The microstructure analysis also demonstrates that with the increase of cement, kaolinite and sodium silicate, the void ratio and porosity of treated soil particles decrease, leading to an increase in the soil density by the hydration, pozzolanic, and polymerisation processes. This research contributes an extra useful knowledge to the stabilisation of organic soils and upgrading such problematic soils closer to the non-problematic soils for geotechnical applications such as deep mixing.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.537-537
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• 2015

In recent decades, the independence and identical distribution (iid) assumption for extreme events has been shown to be invalid in many cases because long-term climate variability resulting from phenomena such as the Pacific decadal variability and El Nino-Southern Oscillation may induce varying meteorological systems such as persistent wet years and dry years. Therefore, in the current study we propose a new parameter estimation method for probability distribution models to more accurately predict the magnitude of future extreme events when the iid assumption of probability distributions for large-scale climate variability is not adequate. The proposed parameter estimation is based on a metaheuristic approach and is derived from the objective function of the rth power probability-weighted sum of observations in increasing order. The combination of two distributions, gamma and generalized extreme value (GEV), was fitted to the GEV distribution in a simulation study. In addition, a case study examining the annual hourly maximum precipitation of all stations in South Korea was performed to evaluate the performance of the proposed approach. The results of the simulation study and case study indicate that the proposed metaheuristic parameter estimation method is an effective alternative for accurately selecting the rth power when the iid assumption of extreme hydrometeorological events is not valid for large-scale climate variability. The maximum likelihood estimate is more accurate with a low mixing probability, and the probability-weighted moment method is a moderately effective option.