• Proceedings of the Korean Institute of Building Construction Conference
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• 2004.05a
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• pp.71-74
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• 2004

Recently, with the wide shortage of natural sand resources, it has been increasingly used the crushed sand. rushed sand is made by the process of crushing the rocks artificially, which has different particle properties compared with that of natural sand. Because such different panicle properties of crushed sand results in an undesirable effects of concrete. improvement technology for crushed sand particle properties like grain shape and fine particle needed during the manufacturing process. In this paper, improvement technology of grain shape and fine particle is reported. According to test results, adequate investment for manufacturing facilities like impact crusher and abrasion test machine is required to meet the advanced grain shape and grading of crushed sand. Based on the investigation of test result, mixing of natural land and crushed sand with given proportion can achieve the improvement of grain shape. For improving excessive fine panicle contents. current manufacturing system also can enhance the existing technology for fine particle without additional investment. It can be concluded that adequate investment and research can improve the quality of crushed sand.

• The Journal of Korea Robotics Society
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• v.12 no.3
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• pp.332-338
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• 2017

As an interpretation of existing jamming effects, the main variables affecting the increase in stiffness due to jamming are known as system density, jamming density, pressure, and particulate temperature. The main variable, jamming density, is closely related to the distribution of particle size and contact properties such as particle shape and friction. However, the complexity of these variables makes it difficult to fully understand the mechanism of the jamming effect. In this paper, we focus on the jamming effects of particles that have more elastic properties than particles such as sand and coffee powder, which are commonly used as constituent particles of existing jamming, in order to reduce complicated factors such as temperature and concentrate on jamming effects based on elastic characteristics of particles. It was experimentally explored the possibility of increasing stiffness by mixing particles of different sizes rather than simply increasing the bending stiffness by controlling the particle size. Through simulations and experiments, we found a case where the stiffness of each particle size distribution is larger than the stiffness of each particle size.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.449-454
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• 2015

The fabrication process of zirconia gel-casting was studied to obtain dense zirconia on a large scale or with complicated shapes. As an experimental parameter, two different particle sizes ($0.1{\mu}m$ and $0.7{\mu}m$) of zirconia powder were applied to the gel-casting process. The viscosity behavior of slurries incorporating 40 vol% of zirconia powder was examined as a function of the dispersant content and the solid load to determine the optimum dispersion conditions. In addition, the gelation time with an initiator, the de-binding behavior, and the main factors affecting densification were examined. The densification of the gel-casted zirconia green body depended on the mixing ratio between the monomer and the dimer and on the zirconia particle size. A green body with a small particle size of $0.1{\mu}m$ showed less densification, with a relative density of 93%. This may be due to the excess number of bubbles created through interactions between the larger particle surface and polymer additives during the ball-milling process.

• Textile Coloration and Finishing
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• v.34 no.4
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• pp.261-271
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• 2022

Waterborne polyurethane(WPU) is greatly affected by its properties depending on the average particle size. In this study, by analyzing the characteristics of WPUs with different average particle sizes according to the DMPA content and we confirmed that the WPU-Ms have different properties from the physical properties of WPU by mixing two types of WPU with different particle sizes in the same volume. At this time, we mixed WPU at an ideal ratio of 7:3 through literature research. In the thermal characteristic analysis, it was confirmed that the thermal decomposition temperature decreased and Tg increased as the content of DMPA, which is the hard segment, increased. In addition, the average particle size of WPU decreased as DMPA increased, and physical properties and adhesive strength were improved due to increased interaction. When mixed with each other in a weight ratio of 7:3, it was observed that adhesion and mechanical properties were improved compared to only WPU.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4213-4227
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• 2023

Computer Automated Radioactive Particle Tracking (CARPT) technique has been successfully utilized to measure the velocity profiles and mixing parameters in different multiphase flow systems where a single radioactive tracer is used to track the tagged phase. However, many industrial processes use a wide range of particles with different physical properties where solid particles could vary in size, shape and density. For application in such systems, the capability of current single tracer CARPT can be advanced to track more than one particle simultaneously. Tracking multiple particles will thus enable to track the motion of particles of different size shape and density, determine segregation of particles and probing particle interactions. In this work, a newly developed Multiple Radioactive Particle Tracking technique (M-RPT) used to track two different radioactive tracers is demonstrated. The M-RPT electronics was developed that can differentiate between gamma counts obtained from the different radioactive tracers on the basis of their gamma energy peak. The M-RPT technique was validated by tracking two stationary and moving particles (Sc-46 and Co-60) simultaneously. Finally, M-RPT was successfully implemented to track two phases, solid and liquid, simultaneously in three phase slurry bubble column reactors.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.209-212
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• 2002

Main radionuclides of the soil waste stored in Korea Atomic Energy Research Institute are Co-60 and Cs-137. Moisture content of soil is 12%, pH of soil is 5.8, and content of organic matter is 2.2 %. Radioactive concentrations of the soil particle size of which is less than 0.063mm and soil in the drum surface of which is more than radiation dose rate 0.05mR/hr are higher. Meanwhile, radioactive concentration of soil in the drum surface of which is less than radiation dose rate 0.02 mR/hr are mostly lower. On using the mixing solution of ammonium sulfate and citric acid, 62% Co was removed from soil and 41% Cs was removed. Also, on using the mixing solution of ammonium nitrate and citric acid, 61% Co was removed from soil and 39% Cs was removed, and on using the mixing solution of ammonium potassium oxalate, 36% Co was removed and only 3% Cs was removed. And on using only water, removal efficiency is less than 5%.

• Journal of Powder Materials
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• v.10 no.5
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• pp.333-336
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• 2003

The purpose of this study is the fabrication of nano-sized Fe-Co alloy powders with soft magnetic properties by the slurry mixing and hydrogen reduction (SMHR) process. $FeCl_2$0 and $CoCl_2$ powders with 99.9% purities were used for synthesizing nanostructured Fe-Co alloy powder. Nano-sized Fe-Co alloy powders were successfully fabricated using SMHR, which was performed at 50$0^{\circ}C$ for 1 h in H$_2$ atmosphere. The fabricated Fe-Co alloy powders showed $\alpha$' phase (ordered body centered cubic) with the average particle size of 45 nm. The SMHR powder exhibited low coercivity force of 32.5 Oe and saturation magnetization of 214 emu/g.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.715-718
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• 2001

This study uses traditional alum coagulation and sedimentation process to treat CMP wastewater from cleaning after polishing. The primary goal is to successfully recycle both solid fines and water for semiconductor manufacturing. Results indicated that CMP wastewater may be successfully treated to recover clean water and fine particles by alum coagulation. The optimum operating conditions for coagulation are as fellowing: alum dosage of 10 ppm, pH at 5, rapid mixing speed at 800 rpm, 5 min rapid mixing time, and long slow mixing time. The treated water with low turbidity and an average residual aluminum ion concentration of 0.23 ppm may be considered for reuse. The settled sludge after alum coagulation contains mainly SiO$_2$particle with a minor content of aluminum (1.7 wt%) may be considered as raw materials for glass and ceramic industry.

• Journal of Korean Society on Water Environment
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• v.21 no.4
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• pp.379-384
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• 2005

In this research, coagulation was employed as the pretreatment for membrane process. The effective coagulation conditions were decided after the discussion of different coagulant doses and mixing conditions, etc. Raw water was taken from Nakdong River. The best operation occurred when G value was $230s^{-1}$ and the slow mixing lasted around 5 minutes at G value was $23s^{-1}$. To investigate the optimum coagulant dosage, the optimum organics removal was target as organic removal reduces membrane fouling effectively than particle removal. This result indicated that organics are more important causes than turbidity for membrane fouling. However, turbidity becomes an important factor after certain amount of organic matters is removed.

• Journal of Mechanical Science and Technology
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• v.16 no.4
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• pp.572-579
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• 2002

The experimental measurements were carried out to examine turbulent disintegration characteristics ejecting from a counter-flowing internal mixing pneumatic nozzle under variable conditions of swirl angles and air pressures. The air injection pressure was varied from 60 kPa to 180 kPa and four counter-flowing internal mixing nozzles with axi-symmetric tangential-drilled holes at swirl angle of 15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$, and 60$^{\circ}$to the central axis have been specially designed. The experimental results were quantitatively analyzed, focusing mainly on the comparison of turbulent atomization characteristics issuing from an internal mixing swirl nozzle. To illustrate the swirl phenomena, the distributions of mean velocities, turbulence intensities, volume flux, and SMD (Sauter Mean Diameter, or D$\sub$32/) were comparatively analyzed.