• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.2
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• pp.141-151
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• 2015

A new rock excavation method using an abrasive injection waterjet system has been developed to enhance the efficiency and reduce the vibration of tunnel excavation. The abrasive feed rate is an important factor for the cutting performance and the economical efficiency of waterjet-based excavation. In this study, various experiments were performed to explore the effects of major process parameters for both the abrasive feed rate and the suction pressure occurring inside the mixing chamber when the abrasives are inhaled. Experimental results reveal that the abrasive feed rate is affected by geometry parameters (abrasive pipe height, length, and tortuosity), abrasive parameters (abrasive particle size), and jet energy parameters (water pressure and water flow rate). In addition, the relation between the cutting performance and the abrasive feed rate was discussed on the basis of the results of an experimental study. The cutting performance can be maximized when the abrasive feed rate is controlled appropriately via careful management of major process parameters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.206-211
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• 2020

Tungsten alloys are used widely in general industrial fields, but they are difficult to cast, so products are manufactured using powder metallurgy. In this study, a mixed powder of tungsten, nickel, and iron homogenized using a ball mill was added to pure water as a solvent, and PVA as a binder was added to prepare a spray drying mixture. The mixed liquid was prepared using a spraying machine. A study was carried out to produce a granular powder that can reduce the variations between products during the molding and sintering process of the powder metallurgy method. A preliminary experiment was conducted to confirm the influence of the variables in the granulation process. Through the preliminary test results, this experiment was performed with the volume of solvent of the spray drying the mixture as an independent variable, and granular powder having a mean particle size similar to that of the existing mass-production conditions and an increased apparent density was prepared. In addition, a pilot test was conducted for the molding and sintering process. The improved granular powder reduced the characteristic variation (weight variation) of the mass-produced product.

• Journal of Korean Neurosurgical Society
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• v.63 no.6
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• pp.698-706
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• 2020

Objective : To study the physiochemical characteristics of podophyllotoxin (PPT) conjugated stearic acid grafted chitosan oligosaccharide micelle (PPT-CSO-SA), and evaluate the ability of the potential antineoplastic effects against glioma cells. Methods : PPT-CSO-SA was prepared by a dialysis method. The quality of PPT-CSO-SA including micellar size, zeta potential, drug encapsulation efficiency and drug release profiles was evaluated. Glioma cells were cultured and treated with PPT and PPT-CSO-SA. The ability of glioma cells to uptake PPT-CSO-SA was observed. The proliferation of glioma cells was determined by 3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay. The apoptosis and morphology of U251 cells were observed by 4',6-Diamidino-2-phenylindole dihydrochloride (DAPI) dye staining. Cell cycle analysis was performed by flow cytometry. The migration ability of U251 cells was determined by wound healing test. Results : PPT-CSO-SA had nano-level particle size and sustained release property. The encapsulation efficiency of drug reached a high level. The cellular uptake percentage of PPT in glioma cells was lower than that of PPT-CSO-SA (p<0.05). The inhibitory effect of PPT-CSO-SA on glioma cells proliferation was significantly stronger than that of PPT (p<0.05). The morphologic change of apoptosis cell such as shrinkage, karyorrhexis and karyopyknosis were observed. The percentage of U251 cells in G2/M phase increased significantly in the PPT-CSO-SA group compared with PPT group (p<0.05). Compared with the PPT group, the cell migration ability of the PPT-CSO-SA group was significantly inhibited after 12 and 24 hours (p<0.05). Conclusion : PPT-CSO-SA can effectively enhance the glioma cellular uptake of drugs, inhibit glioma cells proliferation and migration, induce G2/M phase arrest of them, and promote their apoptosis. It may be a promising anti-glioma nano-drug.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.8
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• pp.1771-1776
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• 2011

In this paper, as an attempt to improve the preparation conditions of $YBa_2Cu_3Ox$ superconducting bulk samples, the properties of $YBa_2Cu_3Ox$ superconductor depending on the particle size of YBCO powder and $BaPbO_3$ as an additive have been investigated, and a study on the effects of additive to the density, grain alignment, and porosity of samples that affect the critical current of superconductor has been performed. In order to prepare superconductor, $YBa_2Cu_3Ox$ powder synthesized by sol-gel method, showing a size distribution of 0.2~1 ${\mu}m$ was used. The $BaPbO_3$ added to promote grain growth and to decrease porosities and weak links between grain boundaries of $YBa_2Cu_3Ox$ superconductors. In the samples prepared by sol-gel synthesized powder with 10, 20, and 30 wt% conductive $BaPbO_3$ additives, the sample with 20 wt% $BaPbO_3$ obtained the highest critical current of 4.74 A, showing 20 wt% higher critical current than that with solid state synthesized powder.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.77-82
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• 2015

Slamming means that the hull hits the waves and receives impact pressure. This slamming effect may cause harm to people and when you put the hull at risk. so it is very harmful for cargo safety. Therefor slamming impact pressure should be fully considered in ship designing. In this study the model of wedged type structure are produced aimed to simulate a free fall that the experiments were carried out on different weight and free fall height. The flow field has been obtained by 2-frame grey level cross correlation PIV(Particle Image Velocimetry) method and experiment was divided into water entry and water exit. The impact pressure of free fall structure by a pressure acquisition system apply to dewetron system. The angles between a model and the water surface are adapted $15^{\circ}$ respectively. The weight change of models was given as 1.5, 1.8 and 2.0kg. To study slamming phenomenon for free fall height the experiments were carried out by the free fall height of 100, 200 and 300mm. The experimental value of the impact pressure according to the changes in weight was increase impact pressure in proportion to the increase in weight and higher free falling height has also influenced the increase in impact pressures.

• The KIPS Transactions:PartB
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• v.12B no.3 s.99
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• pp.273-282
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• 2005

Real-time Object tracking is an important field in developing vision applications such as surveillance systems and vision based navigation. mean-shift algerian and Condensation algorithm are widely used in robust object tracking systems. Since the mean-shift algorithm is easy to implement and is effective in object tracking computation, it is widely used, especially in real-time tracking systems. One of the drawbacks is that it always converges to a local maximum which may not be a global maximum. Therefore, in a cluttered environment, the Mean-shift algorithm does not perform well. On the other hand, since it uses multiple hypotheses, the Condensation algorithm is useful in tracking in a cluttered background. Since it requires a complex object model and many hypotheses, it contains a high computational complexity. Therefore, it is not easy to apply a Condensation algorithm in real-time systems. In this paper, by combining the merits of the Condensation algorithm and the mean-shift algorithm we propose a new model which is suitable for real-time tracking. Although it uses only a few hypotheses, the proposed method use a high-likelihood hypotheses using mean-shift algorithm. As a result, we can obtain a better result than either the result produced by the Condensation algorithm or the result produced by the mean-shift algorithm.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.4
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• pp.210-218
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• 2016

The pollutant removal efficiencies of stormwater runoff by settling were analyzed using field samples collected in 4 different raining events in a test bed installed in the Gwanpyung-Cheon stream in Daejeon. A 1.8 m high with 30 cm diameter cylindrical settling device was used for the settling test by measuring concentration of TSS, TP and TN for time and height. The pollutants removal rate was relatively high in the first 4 hours while 24 hours seem to be necessary to reach steady state in pollutant concentrations. However, there were no considerable differences in concentrations for height at a given time. This indicates most of particulate pollutant in the test seems to show independent settling with no interference to each other. Much part of particle sizes were distributed in the range of $10{\sim}100{\mu}m$. Average particulate fractions of TP and TN were estimated as 52.4% and 23.5%, respectively. This results explain why TN is difficult to remove by simple settling. This study indicates that a simple settling can provide effective method to remove significant amount of TSS and TP effectively and this can be used to protect urban river water quality.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.177-184
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• 2010

When cement grout is used for waterproofing of grounds, important roles are played by fluidity, particle size and bleeding. The most important element which determines their characteristics is the water/cement ratio of grout. Moreover in order to improve the efficiency of soil permeation, micro cement with a smaller average diameter is used in addition to ordinary portland cement. Besides the mixing ratio and cement diameter, the condition of ground is also of fundamental importance in the efficiency of permeation. In order to evaluate grout in terms of permeation ability into ground, we need a field test of grounting, which is cost and time consuming. In this paper we present a laboratory test method in which the suitability and efficiency of grouts are simply and more practically tested. In Korea neither a test standard nor devices are available to simulate grouting in a laboratory. We devised a grout injection equipment in which grouting was reproduced in the same condition with different materials, and suggested a standard for the production of specimens. Our tests revealed that the efficiency of injection increases with the water/cement ratio. We also found that more efficiently injected is the grout with the order of decreasing size; MS8000, micro cement, and ultra fine cements, and colloidal super cement.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• Journal of Life Science
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• v.30 no.2
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• pp.191-201
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• 2020

As society develops rapidly, environmental pollution is becoming a greater risk factor threatening human health. One of the major causes of air pollution that affects human health is particulate matter (PM), which contains a heterogeneous mixture of different particle sizes and chemical compositions. PM is classified by size into general PM (PM₁₀; diameter below 10 ㎛) and fine PM (PM_2.5; diameter below 2.5 ㎛). PM_2.5 can pass through the respiratory tract into the circulatory system and thence throughout the body. PM_2.5 is known to stimulate oxidative stress and inflammatory responses to cells, promoting diseases such as asthma, chronic respiratory disease, cardiovascular disease, diabetes mellitus, and immunological disorders. Although detailed molecular mechanisms for how PM stimulates disease progression still need to be elucidated, together with national efforts to reduce PM production, significant research has been conducted that demonstrates the harmfulness of PM in disease progression through in vitro and in vivo experiments. This review focuses on the harmfulness of PM in disease progression; we also introduce a biological verification method for determining the hazards of PM.