• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.70-77
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• 2010

This study is to investigate experimentally the influence of mixing factors, such as a mortar mix proportion of non-cement mortar, flow, and W/B, on quality characteristics of blast furnace slag powder mortar incorporating dry type recycled fine aggregates. In the characteristics of fresh mortar, the W/B increased according to the increase in the flow due to the increase in water contents, but air contents decreased due to loss of air contrary to the increase in the W/B. In the case of hardened mortar, the compressive strength showed a decrease due to the highly determined W/B inversely according to the increase in the flow through the entire age in which the compressive strength increased proportionally according to the increase in the B/W. Also, the increasing rate of such compressive strength increased more largely due to the latent hydraulic property of the BS according to the passage of the age. The flexural strength at the age of 28 days according to the increase in the B/W represented a similar level in strength values without any increases. The flexural strength for the compressive strength was distributed as a range of 1/2 ~ 1/3 and that showed a higher range than that of conventional concretes.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.224-229
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• 2010

Transparent conductive oxide films have been widely used in the field of flat panel display (FPD). Transparent conductive Indium Zinc Oxide (IZO) thin films with excellent chemical stability have attracted much attention as an alternative material for Indium Tin Oxide (ITO) films. In this study, using $In_2O_3$ and ZnO powder mixture with a ratio of 90 : 10 wt% as a target, IZO films are prepared on polynorbornene (PNB) substrates by electron beam evaporation. The effect of thickness and $O_2$ introduction flow rate on the optical, electrical, structural properties and surface composition of deposited IZO films were investigated by UV/Visible spectrophotometer, 4-point probe method, SEM, XRD and XPS.

• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.676-679
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• 2010

Nano composite particles were synthesized from a bulk ZrVFe alloy ingot by transferred DC thermal plasma. Effects of plasma gas flow rate on the characteristics of the produced nano composite particles were investigated. The characteristics of the synthesized powder were analyzed by field scanning electron microscopy (FE-SEM), light scattering particle size analyzer (PSA), energy dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), and Brunauer-Emmett-Teller (BET) surface area analyzer. As the flow rate of plasma gas increased from 20 L/min to 40 L/min, the average particle size decreased from 91 nm to 55 nm, the particle size distribution became narrower, the surface area increased from $200\;m^2/g$ to $255\;m^2/g$, the particle composition was nearly unaffected, and the particle crystallinity was improved.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.3
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• pp.42-48
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• 2010

The aim of this study is to investigate the influence of driving atomizing nozzle position, the slope of sludge entering tube and supplying air flow rate on the performance of sludge air dryer. This paper deals with optimization of the geometry of the atomizing nozzle for sludge drying using computational fluid dynamics and drying performance test using pilot air dryer. The air drying system was composed of the atomizing nozzle which made high-speed fluid field. dewatered cake was crushed at the high-speed zone as the first step and formed intto dried powder of sphere shape by the collision between particles at the circling zone. The CFD analysis results show when the slope of entering sludge tube is smaller, suction air amount is increased. It is shown that the developed atomizing nozzle is very excellent in the drying performance through pilot test.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.352-361
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• 2006

The grouting method is widely used in construction to reduce permeability and reinforce the ground. If the cement and grout material are not mixed well in the injection tip equipment, an opposite flow and Interception state of the chemical grouting can occur. McG method installs a special grouting device to allow better mixing of the grouting material and prevent backward flow. The block of nozzle also diversify powder rate of cement. YSS that lowers $Na_2O$ and thereby increases durability is developed by gel-forming reaction material. In this study, the seepage state and unconfined compressive strength of the injection material using the special injection tip equipment is tested. The results of laboratory and field tests clearly demonstrate that the strength increases and permeability decreases using the McG method.

• Journal of the Korean Ceramic Society
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• v.33 no.5
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• pp.514-518
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• 1996

Sb doped SnO2(ATO: Antinomy doped Tin Oxide) thin films were prepared by a DC magnetron spttuering method using an oxide target and the electrical characteristics of ATO films were investigated. The experimen-tal conditions are as follows :Ar flow rate ; 0~100 sccm deposition tempera-ture ; 250~40$0^{\circ}C$ DC sputter powder ; 150~550W and sputteing pressure ; 2~7 mTorr, The thickness of depositied ATO films were 600$\AA$~1100 $\AA$ ranges. The resistivity of ATO films was decreased due to the increase of the crystallinity of ATO films with deposition temperature. The decrease of carrier concentration of films with the increase of oxygen flow rate and working pressure is responsible for the increase of resistivity. Increasing of sputtering power raised the resistivity of films by decreasing the carrier mobility.

• Computers and Concrete
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• v.20 no.1
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• pp.77-84
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• 2017

Shirasu, a pyroclastic flow deposit, showed considerable performance as aluminosilicate source in geopolymer, based on past research. However, the polymerization reactivity was somewhat lower compared to the traditional fly ash based geopolymer even though the long-term strength was fairly good. The present study concentrates on the development of higher initial strength performance of Shirasu based geopolymer by utilizing ground granulated blast furnace slag as an admixture. Mortars with various mix proportions were adopted to study the effect of parametric changes on strength development along with the addition of slag in different percentages. A combination of sodium hydroxide and sodium silicate was used as alkaline activators considering parameters like molar ratios of alkali to geopolymer water and silica to alkali molar ratio. The mortars were cured at elevated temperatures under different curing conditions to analyze the effect on strength development. Compressive strength test, mercury intrusion porosimetry and X-ray powder diffraction were carried out to assess the strength performance and microstructure of slag-Shirasu based geopolymer. Based on the experimental study, it was observed that the initial and long-term strength development of Slag-Shirasu geopolymer were improved by the addition of slag.

• Korea-Australia Rheology Journal
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• v.13 no.1
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• pp.47-54
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• 2001

Prediction of the maximum packing volume fraction with non-spherical particles has been one of the important problems in powder technology. The sphericity of fly ash particles depending on the particle diameter was measured by means of a CCD image processing instrument. An algorithm to predict the maximum packing volume fraction with non-spherical particles is proposed. The maximum packing volume fraction is used to predict the slurry viscosity under well dispersed conditions. For this purpose, Simha's cell model is applied for concentrated slurry with wide particle size distribution. Also, Usui's model developed for aggregative slurries is applied to predict the non-Newtonian viscosity of dense fly ash - water slurry. It is certified that the maximum packing volume fraction for non-spherical particles can be successfully used to predict slurry viscosity. The pressure drop in a pipe flow is predicted by using the non-Newtonian viscosity of dense fly ash-water slurry obtained by the present model. The predicted relationship between pressure drop and flow rate results in a good agreement with the experimented data obtained for a test rig with 50 mm inner diameter tube. Base on the design procedure proposed in this study, a feasibility study of fly ash hydraulic transportation system from a coal-fired power station to a controlled deposit site is carried out to give a future prospect of inexpensive fly ash transportation technology.

• Applied Microscopy
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• v.46 no.1
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• pp.45-50
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• 2016

Iron containing a high amount of chromium is known to be inferior to ductility due to ${\sigma}$ phase formation so that it is generally difficult to apply the plastic deformation process although the alloy possesses a superior characteristics of an excellent corrosion resistance. In this study, Fe-50mass%Cr alloy was melted using high purity powder and the deformation behavior has been investigated by cold rolling and tensile test. The tensile test yielded that the alloy revealed a serration at an early stage of tensile deformation and then the serrated flow vanished to change to a normal work hardening flow at the later stage. The former was governed by twin formation process, the latter by dislocation multiplication one, bringing about a high ductility of 20% or over. The reduction ratio in cold rolling was attained as high as 90%, thus the high corrosion-resistant alloy is able to possess a high ductility.

• Transactions of Materials Processing
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• v.12 no.6
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• pp.588-596
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• 2003

The relationships between evolution of microstructure and mechanical properties of porous Al-3Si-2Mg-2Cu alloy after the foaming and various heat treating were investigated. The foamed alloy having various densities were manufactured by powder compact foaming and heat treated. Then compression test was performed with deformation rate of 0.5/s. The ultimate compression strength was not changed after solution heat treatment but the flow curve after ultimate strength showed very smooth and uniform plateau region. This change of flow curve means that the deformation mechanism is altered from brittle fracture to ductile deformation and the energy absorption property of Al foam is dramatically improved. The improvement of energy absorption without any detriment of mechanical properties is due to that the very brittle precipitation like Al-Cu and Al-Mg was uniformly dissolved in Al matrix after solution heat treatment. And various mechanical properties of Al alloy porous material were improved by 40% with aging of $200^{\circ}C$ and 50min. These improvements are ascribe to the various fine precipitates like $\Omega$ and $\theta$'.