• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.678-686
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• 2016

The effect of internal and shroud nozzle distributor to bubbling fluidized beds which has the size of $0.3m-ID{\times}2.4m-high$ column was modeled by CPFD (Computational Particle-Fluid Dynamics). Metal-grade silicon particles (MG-Si) were used as bed materials which have $d_p=149{\mu}m$, ${\rho}_p=2,325kg/m^3$ and $U_{mf}=0.02m/s$. Total bed inventory and static bed height were 75 kg and 0.8 m, respectively. Effect of vertical internal on the bubble rising velocity was investigated. Bubbles were split by internal when the axial position of the internal from the distributor, z = 0.45 m. Bed pressure drop and axial solid holdup were not affected by internal. However, in the case that axial distance of internal from distributor was too close to jet penetration length, bubbles were not separated and bypassed internal, and faster than without internal or z = 0.45 m.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.260-270
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• 2017

Zirconia has white color and physical, chemical stability, also using in high temperature materials and various industrial structural ceramics such as heat insulating materials and refractories due to their low thermal conductivity, excellent strength, toughness, and corrosion resistance. If hydrophobically modified zirconia is introduced into a hydrophobic acrylate coating solution, the hardness, chemical, electrical, and optical properties will be improved due to the better dispersibility of inorganic particle in organic coating media. Thus, we introduced $-CH_3$ group through silylation reaction using either trimethylchlorosilane(TMCS) or hexamethyldisilazane(HMDZ) on zirconia surface. The $Si-CH_3$ peaks derived from TMCS and HMDZ on hydrophobically modified zirconia surface was confirmed by FT-IR ATR spectroscopy, and introduction of silicon was confirmed by FE-SEM/EDS and ICP-AES. In addition, the sedimentation rate result in acrylate monomer of the modified zirconia showed the improved dispersibility. Comparison of the sizes of a pristine and the modified zirconia particles, which were clearly measured not by the normal microscope but by particle size analysis, provided a pulverizing was occurred by physical force during the silylation process. From the BET analysis data, the specific surface area of zirconia was approximately $18m^2/g$ and did not significantly change during modification process.

• Journal of the Korean Geotechnical Society
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• v.31 no.1
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• pp.37-46
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• 2015

In this study, a blast furnace slag with the alkaliphilic microorganism (Bacillus halodurans) alkaline activator was used to cement natural soils in the field. A low-cost and massive microbial solution for cementation of field soils was produced and compared with existing microbial culture in terms of efficiency. A field soil was prepared for three different cementation areas: a cemented ground with microbial alkaline activator (Microbially-treated soil), a cemented ground with ordinary Portland cement (Cement-treated soil), and untreated ground (Non-treated soil). The testing ground was prepared at a size of 2.6 m in width, 4 m in length, and 0.2 m in depth. After 28 days, a series of unconfined compression tests on the cement-treated and microbially-treated soils were carried out. On the other hand, a torvane test was carried out for non-treated soil. The strength of field soils treated with microorganism was 1/5 times lower than those of cement-treated soil but is 6 times higher than non-treated soil. The pH measured from microbially-treated soil was about 10, which is lower than that of cement-treated soil (pH = 11). Therefore, it is more eco-friendly than Portland cemented soils. The C-S-H hydrates were found in both cement- and microbially-treated soils through SEM-EDS analyses and cement hydrates were also found around soil particles through SEM analysis.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.40-46
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• 2013

Based on Korean railway design standards, the thicknesses of the reinforced roadbeds of conventional and high speed railways are different, and so too, for the size distribution of the ballast particles. Accordingly, considerable cost would be required to increase operating speeds of conventional lines, in particular related to changing from a ballasted track system to a ballastless one. In this study, applicability of a roadbed which supports conventional ballasted track, for use as a ballastless track for a high speed rail line was examined. A reinforced roadbed for a conventional railway is 20cm thick, and the type of material used for a conventional reinforced roadbed is M-40 (crushed gravel for road embankments). A dynamics test was conducted to evaluate the occurrence of the permanent settlement of the track substructure. These results suggest that, without changes to the track substructure, an operational speed of 400km/h is feasible with a ballastless track. This result; however, is from laboratory experiments. Further studies, such as numerical analyses or field validation, are required.

• Membrane Journal
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• v.28 no.4
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• pp.252-259
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• 2018

An acidic, real metal-plating wastewater was treated by a fluidized bed membrane reactor introduced with granular activated carbon (GAC) as fluidized media. With GAC fluidization, there was no increase in suction pressure with time at each flux set-point applied. At neutral solution pH, much less fouling rate was observed than acidic pH under GAC fluidization. Higher solution pH resulted in the increase in particle size in metal-finishing wastewater, thus producing a less dense cake structure on membrane. More than 95% of chemical oxygen demand was observed from the fluidized bed membrane reactor under GAC fluidization. Total suspended solid concentration in membrane permeate was near zero. At the raw wastewater pH, no removal of copper and chromium by the fluidized bed membrane reactor was observed. As the pH was increased to 7.0, removal efficiency of copper and chromium was increased considerably to 99 and 94%, respectively. Regardless of solution pH tested, more than 95% of cyanide was removed possibly due to the strong adsorption of organic-cyanide complex on GAC in fluidized bed membrane reactor.

• Archives of design research
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• v.14 no.3
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• pp.197-210
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• 2001

There are symbolicity and special meaning in the materials which are supposed to be used metalcraft from ancient to present. These are basical resources of hermeneutics and play a role as moaning elements. Generally, the precious Cold and Silver are mainly to be used with precious stone. But recently, ordinary materials like glass iron aluminum has begun to be used with them. Several artists are intentionally using them, and special skills which could be revealed by only the matherials are developing by them. In these skill, there are original material's texture and character of matter are looking like other matter. Well, special skills are adapted in these matters to magnify the possibility of expression, the originally codified meaning resources are disturbed. For example, The metal craft artist June Schwarcz is using the skills of electroforming, copper foiling, enameling, wire brush patina, fine wires fusing, etc. He is doing abstract forming and making various textures. And his works are very big size, and done by the skills of painting and sculpture. The outer form is very structural, special touches of the artists are heterogeneously mixed with the symbolic abstract expressionism color field. Further, there are mixed with Primitive original life atmosphere, Medieval ornamental aspect, Minimal, and Chaotic aspects. The meaning particles of these aspects are directly/indirectly joined but special skills and basic material languages are mixed together, the originally codified material language are disturbed. These disturbed material languages are becoming optically special effect and be illusion. It is making expressing way of tile metalcraft more fertile and be infinite.

• Journal of the Mineralogical Society of Korea
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• v.20 no.2 s.52
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• pp.135-145
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• 2007

The needs for the ultra fine particles have been increased in preparation field of raw powders such as fine ceramics and high functional products. In this study, a series of wet grinding experiments were carried out on inorganic powders such as calcite, pyrophyllite and talc by a stirred ball mill. The particle size distribution of ground products of each test material fur a given grinding time was found to be expressed by the grinding rate (selection function) which was obtained from the grinding kinetics analysis. The median diameter decreased from 6.49 to $0.47{\mu}m$ in calcite, and decreased from 3.91 to $1.14{\mu}m$ in pyrophyllite. However, in talc, median diameter was decreased a little bit from 10.30 to $6.67{\mu}m$. The grinding rate changing on calcite and pyriphyllite were similar at the same conditions. However, in the case of talc, it was observed that the grinding rate was not increased compared to other samples.

• Journal of Hydrogen and New Energy
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• v.11 no.4
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• pp.161-169
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• 2000

In the case of photocatalytic hydrogen production from water, the performance-property relationships of CdS-TiO2 film type composite catalysts were investigated. To control the physical properties of the primary particles, the mixture of CdS and TiO2 nano-sols prepared by the sol-gel method at room temperature was hydrothermally treated at 240oC for 12hr. The film electrodes were prepared by the casting method. The photocurrents measured by a photoelectrochemical method and the hydrogen production rates measured by a photochemical method were closely dependent on the physical properties such as crystalline form, primary particle size and CdS/TiO2 mole ratio, and these varied in the range of 1.2~2.6 mA/cm2 and $1.0{\sim}1.6{\times}10-3mol/hr$, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.597-604
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• 2016

The aim of this study was to prevent the decrease in crop output by disease and insect pests and excessive spraying of agricultural pesticides by application uniformity. A 3m height and 15km/h speed is difficult to maintain with an unmanned helicopter for aerial application, which has been affected by the controlling habits and methods or environmental factors, such as changes in the wind. Therefore, in this study, an aerial application system was design to be attached to an unmanned helicopter, which can allow a controlled application width and spray rate automatically and verified experimentally using Rmax of MS-AVIATION. The size of agricultural land was 50 m2 and nine water sensitive cards were arranged at 1.25m intervals in 5 rows with each row having a 10m interval from the position of 5m. The unmanned helicopter was flying at speeds ranging from 7.2km/h to 17.6km/h and heights ranging from 2.32m to 3.47m. The proposed aerial application system allowed application uniformity by making a valid spraying area of 7.5 m2 with 46423 particles distributed on average.

• Journal of Energy Engineering
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• v.13 no.4
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• pp.281-290
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• 2004

Spent refractories from a coal gasifier after 1000 hours of operation were analyzed for crystalline phases, chemical composition and microstructures as a function of slag penetration depth, and the slag corrosion mechanism was determined. The chemical corrosion of chromia refractory occurred via reaction between Cr$_2$O$_3$ of the refractory and FeO and A1$_2$O$_3$ in the slag. The FeO reacted with Cr$_2$O$_3$ at the slare/refractory interface and formed FeCr$_2$O$_4$. After all FeO were consumed, Al in the penetrating slag substituted Cr in Cr$_2$O$_3$, forming (Al, Cr)$_2$O$_3$, at the edges of the particle, which were broken to form fragments rich in Al. The corrosion resistance of Cr$_2$O$_3$ varied with the particle size and the extent of sintering, and the higher resistance was observed in the larger and more sintered particles. There was no chemical change in ZrO$_2$, but showed the effects of physical corrosion: the grain boundaries became more wavy, and ZrO$_2$ grains were split in the corroded area. The slag penetration depth increased in the refractory samples farther down from the feed nozzles.