• Tunnel and Underground Space
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• v.17 no.2 s.67
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• pp.128-138
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• 2007

At low in-situ stress, the continuity and distribution of natural fractures in rock mass predominantly control the failure processes. However at high in-situ stress, the failure process are affected and eventually dominated by stress-induced fractures preferentially growing parallel to the excavation boundary. This fracturing is often observed in brittle type of failure such as slabbing or spatting. Recent studies on the stress- or excavation-induced damage of rock revealed its importance especially in a highly stressed regime. In order to evaluate the brittle failure around a deep underground opening, physical model experiments were carried out. For the experiments a new tue triaxial testing system was made. According to visual observation and acoustic emission detection, brittle failure grades were classified under three categories. The test results indicate that where higher horizontal stress, acting perpendicular $(S_{H2})$ and parallel $(S_{H1})$ to the axis of the tunnel respectively, were applied, the failure grade at a constant vertical stress level (Sy) was lowered. The failure initiation stress was also increased with the increasing $S_{H1}\;and\;S_{H2}$. From the multi-variable regression on failure initiation stress and true triaxial stress conditions, $f(S_v,\;S_{H1},\;S_{H2})$ was proposed.

• Journal of Wetlands Research
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• v.15 no.3
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• pp.387-396
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• 2013

Non-point pollution source is difficult to control due to uncertain outflow path and emission. So, There are many development and research to Best Management Practices(BMP) established to manage the Non-point pollution source. Besides, various methods of estimated efficiency to exact assessment of BMP is presented. In this study, the impact about length of Grassed Swale on reduction efficiency based on monitoring results of Grassed Swale by length is studied. By estimating Grassed Swale reduction efficiency in a variety of methods, the difference between the methods of estimated efficiency was compared with those that. Estimated efficiency method using ER, SOL, ROL, ROF, SOLF, and ROLF methods is analyzed. EMC analysis result is high inflow and outflow concentration distinction organic compound for nutritive salts The result of efficiency analysis along Grassed Swale length sharply increases in a Grassed Swale inlet. After this increase, the efficiency gradually decreases. This is expected that cistern installed in the end of the front. To obtain a stable reduction efficiency of Grassed Swale, minimum length 30m of Grassed Swale should be enough. Also, in order to efficiently and economically design Grassed Swale, the researches on length of Grassed Swale are needed rather than simple analysis of efficiency.

• Journal of Veterinary Clinics
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• v.31 no.6
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• pp.502-506
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• 2014

Recently nano particles have proven for wide array of bioactive properties. In the present study, antibacterial properties of chitosan silver nano composites (CAgNCs) were investigated against fish pathogenic Edwardsiella tarda. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of CAgNCs against E. tarda were $25{\mu}g/mL$ and $125{\mu}g/mL$, respectively. The field emission scanning electron microscope (FE-SEM) image of CAgNCs treated E. tarda showed the strongly damaged bacteria cells than non-treated bacteria. Furthermore, treatment of CAgNCs induced the level of intracellular reactive oxygen species (ROS) in E. tarda cells in concentration and time dependent manner suggesting that it may generate oxidative stress leading to bacterial cell death. In addition, MTT assay results showed that the lowest cell viability at $100{\mu}g/mL$ of CAgNCs treated E. tarda. Overall results of this study suggest that CAgNCs is a potential antibacterial agent to control pathogenic bacteria.

• Korean Journal of Food Science and Technology
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• v.48 no.1
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• pp.92-95
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• 2016

Ultra-high pressure (UHP) was applied to glutinous rice (Dongjin) and brown rice (Shindongjin) to determine its effects on the textural characteristics of cooked rice and bacterial reduction in uncooked rice. Hardness and stickiness of the cooked glutinous and brown rice pretreated with 500 MPa for 5 min were significantly attenuated compared to that of the control rice (p<0.05). After the UHP treatment, particles of the glutinous and brown rice were observed to be finer when cross sections of the rice were analyzed using field emission scanning electron microscope. The total bacterial count in the brown rice treated with 600 MPa for 5 min was reduced from $10^7CFU/g$ to $10^4CFU/g$, while the number of thermoduric bacteria in the brown rice was not significantly different after the UHP treatment. These results suggest that UHP may be an effective method for improving texture of dried rice and to reduce bacterial count in raw rice.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.399-404
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• 2021

From 1 January 2020, the limit for Sulphur in fuel oil used on board ships operating outside designated emission control areas will be reduced to 0.5 %. This regulation by international maritime organization (IMO) is able to significantly reduce the amount of Sulphur oxides (SOx) discharging from ships and should have environmental advantages and health for all over the world. To meet the regulation, in these days, wet scrubber system is being actively developed. However, this process leads to make washing wastewater. In this study, we evaluated ion exchange resin system in accordance with scrubber wastewater discharge regulation by IMO. Theoretical wastewater used as feed solution of lab scale water treatment systems. The results revealed that nitrate ion was removed selectively in spite of high TDS wash wastewater solution depending on ion exchange resin property. Moreover, it was possible to improve efficiency of the system by optimizing operating conditions.

• Journal of the Korean Society of Radiology
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• v.15 no.7
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• pp.935-942
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• 2021

Involuntary movement of internal organs by respiration is a factor that greatly affects the results of radiotherapy and diagnosis. In this study, a moving phantom was fabricated to simulate the movement of an organ or a tumor according to respiration, and ¹⁸F-FDG PET/CT scan images were acquired under various respiratory simulating conditions to analyze the movement range of the tumor movement by respiration, the level of artifacts according to the size of the tumor and the maximum standardized uptake value (SUVmax). Based on Windows CE 6.0 as the operating system, using electric actuator, electric actuator positioning driver, and programmable logic controller (PLC), the position and speed control module was operated normally at a moving distance of 0-5 cm and 10, 15, and 20 reciprocations. For sphere diameters of 10, 13, 17, 22, 28, and 37 mm at a delay time of 100 minutes, 80.4%, 99.5%, 107.9%, 113.1%, 128.0%, and 124.8%, respectively were measured. When the moving distance was the same, the difference according to the respiratory rate was insignificant. When the number of breaths is 20 and the moving distance is 1 cm, 2 cm, 3 cm, and 5 cm, as the moving distance increased at the sphere diameters of 10, 13, 17, 22, 28, and 37 mm, the ability to distinguish images from smaller spheres deteriorated. When the moving distance is 5 cm compared to the still image, the maximum values of the standard intake coefficient were 18.0%, 23.7%, 29.3%, 38.4%, 49.0%, and 67.4% for sphere diameters of 10, 13, 17, 22, 28, and 37 mm, respectively.

• Journal of Life Science
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• v.31 no.10
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• pp.960-968
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• 2021

Since microalgae research started on late 18 century, they have been recognized as one of the most important bioresources used in bioindustry. Owing to the large efforts paid to industrial application of this microorganisms, their importance on food/feed and bioactive compounds has been further extending into the environmental research areas including alternative energy resources, mitigation of the carbon emission, and waste-water treatment. However, despite the importance on their industrial application, the fundamental research field related to the long-term preservation of microalgae culture has not received much attention. However, a less labor intensive and cost-efficient preservation technology enabling biologically active and stable microalgae-culture provides a key success factor in the biotechnological application. Therefore, this study investigated various cutting-edge microalgae cryopreservation technologies currently developed so far, mainly targeting Chlorophyta, which occupies the largest taxon in the classification system of microalgae. In addition, for the development of successful cryopreservation technique, the key factors such as temperature control effect and preservative effect during cryopreservation of microalgae culture were investigated. In addition, the problems with current preservation technology that is being used in Korean domestic biological resource banks and the international microalgal resource banks are described. According to our investigation, currently no standard method for long-term preservation of microalgae is available due to their various morphological and physiological characteristics. To overcome such issues, much more efforts on fundamental research area on the identification of specific biomarker used for microalgae taxonomical classification and further systemic approaches based on strain-specific cryopreservation methods needed.

• Laboraroty Animal Research
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• v.34 no.4
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• pp.248-256
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• 2018

O-2-$^{18}F$-fluoroethyl-l-tyrosine ($[^{18}F]FET$) has been widely used for glioblastomas (GBM) in clinical practice, although evaluation of its applicability in non-clinical research is still lacking. The objective of this study was to examine the value of $[^{18}F]FET$ for treatment evaluation and prognosis prediction of anti-angiogenic drug in an orthotopic mouse model of GBM. Human U87MG cells were implanted into nude mice and then bevacizumab, a representative anti-angiogenic drug, was administered. We monitored the effect of anti-angiogenic agents using multiple imaging modalities, including bioluminescence imaging (BLI), magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET/CT). Among these imaging methods analyzed, only $[^{18}F]FET$ uptake showed a statistically significant decrease in the treatment group compared to the control group (P=0.02 and P=0.03 at 5 and 20 mg/kg, respectively). This indicates that $[^{18}F]FET$ PET is a sensitive method to monitor the response of GBM bearing mice to anti-angiogenic drug. Moreover, $[^{18}F]FET$ uptake was confirmed to be a significant parameter for predicting the prognosis of anti-angiogenic drug (P=0.041 and P=0.007, on Days 7 and 12, respectively, on Pearson's correlation; P=0.048 and P=0.030, on Days 7 and 12, respectively, on Cox regression analysis). However, results of BLI or MRI were not significantly associated with survival time. In conclusion, this study suggests that $[^{18}F]FET$ PET imaging is a pertinent imaging modality for sensitive monitoring and accurate prediction of treatment response to anti-angiogenic agents in an orthotopic model of GBM.

• Clean Technology
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• v.25 no.1
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• pp.19-32
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• 2019

As regional air pollution gets worse by the sulfur oxides emitted from various types of vessels passing through the many countries, the International Maritime Organization establishes the emission control areas and regulates sulfur dioxide in those areas. In order to satisfy these regional regulations, the fuel selection method and the exhaust gas post-treatment device are applied to the ships. Due to the economic reasons, the post-treatment method of exhaust gas for reducing the amount of sulfur oxides discharged is mainly preferred. The scrubber which is dominantly used in the ships are the spray type system where the sprayed liquid drops used for capturing the soluble sulfur dioxides in the exhaust gas. The performance of the spray type system depends on the size distribution of the sprayed droplets. In order to evaluate this performance, we designed counterflow type scrubber and cyclone scrubber and evaluated the desulfurization efficiency and the amount of droplet evaporation according to the size of each droplet by using computational fluid dynamics. The Eulerian-Eulerian analysis method was used because the scrubber had a gas-liquid two-phase flow inside the scrubber. When the diameter of the droplet was $100{\mu}m$, $300{\mu}m$, $500{\mu}m$ and $700{\mu}m$. As a result, both of scrubbers showed high desulfurization efficiency and low evaporation amount at $500{\mu}m$ and $700{\mu}m$.

• Journal of Environmental Impact Assessment
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• v.28 no.2
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• pp.141-151
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• 2019

Korea has passed the Act on the Integrated Control of Pollutant-Discharging Facilities in 2015, and the integrated environmental management under the BAT standard is underway. To summarize the nature of integrated environmental management, it is the regulation by the integration of the management of the multi-pollutant source and the technical standard of BATs. In general, in environmental economics, regulation-based on technical standards are known to be inefficient. This paper attempts to evaluate the efficiency of BAT standards from an economic point of view. A simple multi-pollutant model demonstrates that the inefficiency of the environmental tax with imperfect information in a single pollutant situation is amplified under multi-pollutant conditions. The simultaneous introduction of BAT and IPPC can be partially explained by this logic. It is also highlighted by the strengthening of BAT standards by EU, as a countermeasure to the potential deterioration of air quality caused by the change of effective environmental taxes accompanying the fuel and emission price changes.