• Journal of the Korean Applied Science and Technology
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• v.36 no.2
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• pp.609-622
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• 2019

When the surfactant is dissolved in an aqueous solution, it forms aggregate called micelles (<20 nm) in the solution, and micelles can form the solubilized formulation by supporting the active ingredient therein. Swollen micelles are formulations capable of carrying larger amounts of active ingredient than conventional solubilized formulations at 50~100 nm. Unlike liposomes or nanoemulsions, which require a separate process such as high pressure emulsification, Swollen micelle is a more efficient method of solubilization and particle formation from a productive point of view. In this study, stabilization experiments on swollen micelle formulations were carried out using poloxamer 407, and then optimized formulation experiments for tocopheryl acetate components were performed using Response Surface Methodology (RSM). Tocopheryl acetate, a surfactant that affects solubilization and an active substance, were set as a factor and the correlation between them was confirmed. As the evaluation method, stability and particle size distribution and size were confirmed by temperature and time, and the structure and shape of the swollen micelle carrying the active ingredient were confirmed by FIB. These results show that poloxamer 407 0.500%, octyldodeceth-16 0.387% and tocopheryl acetate 0.945% are the most optimized prescriptions for swollen micelle stabilized with tocopheryl acetate.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.5
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• pp.581-588
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• 2019

A long-term trend analysis of cold water masses along eastern coast of South Korea was performed during summer, based on wind speed, wind direction, and sea surface temperature (SST) data. Wind data collected over a 22-year period (1997-2011) were compared with another set of data collected over the successive 7-year (2012-2018), highlighting a general decrease in the frequency and speed of south winds. However, both the frequency and speed of these winds have been higher in June between 2012-2018, rather than between 1997-2011. The cold water season between July and August was faster during the 7-year period; moreover, the SSTs registered around Gangneung (EN) rose by $0.5^{\circ}C- 1.8^{\circ}C$, while those around Yeongdeok (EC) and Gijang (ES) increased by only $0.1^{\circ}C-0.3^{\circ}C$. The number of cold water days during the 7-year period, compared to those recorded during previous years (1990-2011, satellite SST data by NOAA/AVHRR), decreased in the proximity of Yeongdeok and Gijang, but increased in the proximity of Kangneung. Additionally, the number of cold water days around Kangneung, Yeongdeok, and Gijang increased in June highlighting a geographical and temporal change in the occurrence of cold waters. These observation can be explained by variations in the pressure distribution that should have weakened the East Asian monsoon, affecting the direction and speed of winds that regulate the flow of cold waters.

• Journal of The Korean Society For Urban Railway
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• v.6 no.4
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• pp.319-326
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• 2018

The safety interval to prevent collision between trains in a train control system is based on the braking distance according to the emergency braking of the train. The evaluation of the braking performance is based on the longitudinal train dynamics or the commissioning test in the test track, but since the conditions such as the weakening of the adhesion coefficient between the wheel and rail can not all be considered, these conventional methods are not sufficient to design of the train control systems. Therefore, in this study, the Monte Carlo Method (MCM) which can consider various environments is used to analyze braking performance and limitations. The braking model is based on the air braking used in the emergency braking and is modeled to take into account the braking pressure, efficiency, friction coefficient, adhesion condition, and vehicle mass distribution. It is confirmed that braking performance can be improved by controlling the quality of braking device. In addition, the change of the braking performance was confirmed according to the vehicle constituting the train. The results of this study are expected to be used as basic information for designing safety clearance for the train control systems and as a basis for improving the braking performance of railway vehicles.

• Journal of the Korean Applied Science and Technology
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• v.38 no.5
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• pp.1325-1334
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• 2021

This study reports the development of a manufacturing method of synthesizing colloidal gold using catalysts available for cosmetics and an anti-aging ampoule with skin improvement effects using it. Nano-colloidal gold was synthesized by using ascorbic acid and sodium borohydride as a reducing catalyst in hydrogen tetrachloroaurate tetrahydrate. It was confirmed that the particles became smaller as the mass of the content of ascorbic acid, which is a catalyst, increased. On the other hand, as the mass of sodium borohydride increased, the particle size tended to increase. In order to control the colloidal gold reaction rate, particles having 100 to 500 nm of a particle diameter distribution could be obtained using xanthan gum and hydroxyethylcellulose. The optimal synthesis conditions could be obtained by reacting for 1 to 4 hours at 18℃, a reduced pressure state of 20 to 75 mmHg, a stirring speed of 10~50 rpm. The synthesized colloidal gold had a unique smell of dark pink, pH = 5.5, specific gravity of 1.0032, and viscosity of 80 to 310 cps. As an application of skin care cosmetics, anti-aging ampoule has been developed, and it is expected to be used for various prescriptions and formulations using it.

• Tunnel and Underground Space
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• v.31 no.4
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• pp.270-288
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• 2021

We proposed a numerical method to simulate the hydro-mechanical behavior of rock fracture using a grain-based distinct element model (GBDEM) in the paper. As a part of DECOVALEX-2023 Task G, we verified the method via benchmarks with analytical solutions. DECOVALEX-2023 Task G aims to develop a numerical method to estimate the coupled thermo-hydro-mechanical processes within the crystalline rock fracture network. We represented the rock sample as a group of tetrahedral grains and calculated the interaction of the grains and their interfaces using 3DEC. The micro-parameters of the grains and interfaces were determined by a new methodology based on an equivalent continuum approach. In benchmark modeling, a single fracture embedded in the rock was examined for the effects of fracture inclination and roughness, the boundary stress condition and the applied pressure. The simulation results showed that the developed numerical model reasonably reproduced the fracture slip induced by boundary stress condition, the fracture opening induced by fluid injection, the stress distribution variation with fracture inclination, and the fracture roughness effect. In addition, the fracture displacements associated with the opening and slip showed good agreement with the analytical solutions. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study experiments.

• Geomechanics and Engineering
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• v.28 no.3
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• pp.299-311
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• 2022

Water-resisting key stratum (WKS) between coal seams is an important barrier that prevents water inrush from goaf in roof under multi-seam mining. The occurrence of water inrush can be evaluated effectively by analyzing the fracture of WKS in multi-seam mining. A "long beam" water inrush mechanical model was established using the multi-seam mining of No. 2+3 and No. 8 coal seams in Xiqu Mine as the research basis. The model comprehensively considers the pressure from goaf, the gravity of overburden rock, the gravity of accumulated water, and the constraint conditions. The stress distribution expression of the WKS was obtained under different mining distances in No. 8 coal seam. The criterion of breakage at any point of the WKS was obtained by introducing linear Mohr strength theory. By using the mechanical model, the fracture of the WKS in Xiqu Mine was examined and its breaking position was calculated. And the risk of water inrush was also evaluated. Moreover, breaking process of the WKS was reproduced with Flac3D numerical software, and was analyzed with on-site microseismic monitoring data. The results showed that when the coal face of No. 8 coal seam in Xiqu Mine advances to about 80 m ~ 100 m, the WKS is stretched and broken at the position of 60 m ~ 70 m away from the open-off cut, increasing the risk of water inrush from goaf in roof. This finding matched the result of microseismic analysis, confirming the reliability of the water inrush mechanical model. This study therefore provides a theoretical basis for the prevention of water inrush from goaf in roof in Xiqu Mine. It also provides a method for evaluating and monitoring water inrush from goaf in roof.

• Journal of the Korea Society of Computer and Information
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• v.26 no.4
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• pp.119-131
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• 2021

In this study, I compared the pattern design method of classic shirts focused on the men's clothing consturction textbook. It was intended to select a shirt pattern drawing method suitable for men in their 20s by conducing a appearance evaluation with a 3D simulation program. Pattern drawing method, sizes, appearance evaluation, garment pressure. were evaluated, and SPSS 26.0 program was used for analysis. According to the Pattern drawing method, there were differences in application sizes, and there were many parts where designated sizes were applied. The shirt pattern is mostly the same for the front chest and back chest, front waist and back waist. However, if there is a front and back difference of the chest and the waist circumference, the fit was considered better. B pattern was evaluated as the best in appearance evaluation, color distribution, and mesh condition through 3D simulation, and B pattern was analyzed as the most suitable method for men in their 20s. Since this study applied the average sizes of the 7th Korean Human Body Dimension Survey report in 20s, it is thought that caution should be paid to apply them to all 20s. In the future, it is also thought that research on the actual fit and patterns of various body types and materials in their 20s should be carried out.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.129-137
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• 2008

An active application of concrete track is being expected far the future constructions of Korean railroad. In comparison with the existing ballasted tract, a concrete track is very susceptible for the settlement, since its rehabilitation requires much time and cost. When a concrete track is constructed on fine-grained subgrade soil, excessive cumulative plastic settlements due to repetitive train road may occur. In this case, the settlement of the concrete track may be effectively reduced by installing a small number of small-diameter piles beneath the track. This paper presents the effect of pile installation on the reduction of cumulative plastic settlement of concrete track. A method combining experiential equation and numerical method is proposed. Using an existing experiential equation and the estimated earth pressure distribution, the cumulative plastic strain was calculated. From the results, it is verified that the effects of the pile installation is significant to effectively reduce the cumulative plastic settlement of concrete track. The reduction effects of the cumulative plastic settlement according to the pile number and pile arrangement are presented.

• Journal of Environmental Impact Assessment
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• v.32 no.6
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• pp.503-515
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• 2023

The disconnection and fragmentation of ecological spaces that occur during the development process pose a significant threat to biodiversity. Urban center areas with high development pressure are particularly susceptible to low connectivity due to a scarcity of ecological space. This issue tends to be more pronounced in larger cities.To address this challenge, continuous efforts are needed to assess and improve the current state of ecological space connectivity at the level of individual projects and urban management. However, there is a lack of discussion regarding the analysis and improvement of ecological connectivity in metropolitan cities In line with this objective, this study evaluated the connectivity of ecological spaces in the city centers of Seoul, Busan, Daegu, Incheon, Gwangju, Daejeon, and Ulsan. The evaluation revealed that city centers exhibited lower connectivity of ecological spaces compared to their peripheries or the overall city. In addition, in the ecological network analysis that reflected regional characteristics, such as the species distribution model conducted on Daejeon, 510 optimal paths connecting forests of more than 1ha were derived. This study is significant as an example of deriving an ecological network based on regional characteristics, including quantitative figures necessary for establishing goals to improve urban ecological connectivity and biodiversity. It is anticipated that the results can be utilized to propose directions for enhancing ecological connectivity in environmental impact assessments or urban management and to establish an evaluation framework.

• Clean Technology
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• v.29 no.4
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• pp.272-278
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• 2023

There is a lot of interest in methods for pollutants using adsorption, and recent research is being conducted to show that biochar can be used to remove organic and inorganic pollutants. In particular, wood waste as waste biomass requires a biomass recycling method, and a method to increase the adsorption capacity of biochar produced using wood waste is needed. Biochar is created by Hydrothermal carbonization (HTC) using, which uses low temperature and high pressure, has low energy consumption and does not require moisture removal pretreatment, and biochar is created through chemical activation using KOH, NaOH, and ZnCl₂ chemicals. The adsorption characteristics of biochar were determined by analyzing iodine adsorptivity, specific surface area, pore diameter, pore volume, pore distribution, and SEM according to the activation. The results of analyzing the selecting biochar by activating the biochar produced at HTC 300℃, 4 hr by KOH, NaOH, and ZnCl₂ chemicals, the specific surface area was 774~1.387 m²/g, showing a high specific surface area similar to activated carbon, and it was confirmed that micropores with an average pore diameter in the range of 21~24 Å were formed. As a result of SEM observation, the surface was uniform with a certain shape depending on activation. It was confirmed that one pore was developed and the number of pores increased.