• 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 International Area Studies (JIAS)
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• v.22 no.2
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• pp.305-330
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• 2018

The purpose of this article is to examine whether Myanmar's experience in which dealing with the most exemplary change among rogue states or pariah state in the 21st century is feasible for North Korea's case. Recently, North Korea's willingness to dialogue, reform and open is similar to the precedent in which the Myanmar military junta dismantled its ruling system and turned over transition period through general elections in 2010 and 2015 each. The so-called 'Myanmar Model' refers to a country branded as a rogue state which has been under the international sanctions and pressure, and opening its political system and the market by choosing transformation. However, rapid changes in speed across the entire society after opening up are impossible because the political elite is only the leading role and implementation in the transition. In case of Myanmar, military culture has penetrated into society due to such a long-lasting military dictatorship, and even democratic bloc has become accustomed to authoritarian decision-making process. Furthermore, the "reserved area" of the old regime still exists in a deformed political structure that can not retrieve the interests of the military. Therefore there could not be achieved political development in term of qualification. North Korea also appears unlikely to achieve political and economic assessment in a short period of time, as civil society has not appeared due to its long dictatorship and very low economic development levels. Like Myanmar, North Korea is also likely to control the pace and direction of upcoming reforms and open, as the dictator or most powerful person chose to reform and open up. Therefore, if North Korea moves toward the 'Myanmar Model', there will be high expectations of new changes in the short term, but it could be delayed or stalled in the mid and long term.

• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.21-31
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• 2018

Bucket foundations are widely used in offshore areas due to their various benefits such as easy and fast installations. A bucket is installed using self-weight and the hydraulic pressure difference across the lid generated by pumping out water from inside the bucket. When buckets are installed in high permeable soil such as sands, upward seepage flow occurs around the bucket tip and interior, leading to a decrease in the effective stress in the soil inside the buckets. This process reduces the penetration resistance of buckets. However, the soil inside and outside the bucket can be disturbed due to the upward seepage flow and this can change the soil properties around the bucket. Moreover, upward seepage flow can create significant soil plug heave, thereby hindering the penetration of the bucket to the target depth. Despite of these problems, soil disturbance and soil plug heave created by suction installation are not well understood. This study aims to investigate the behavior of soil during suction installation. To comprehend the phenomena of soil plug heave during installation, a series of small-scale model tests were conducted with different testing conditions. From a series of tests, the effects of tip thickness of bucket, penetration rate, and self-weight were identified. Finally, soil properties inside the bucket after installation were approximated from the measured soil plug heave.

• Clean Technology
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• v.25 no.3
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• pp.206-222
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• 2019

Recently, various multiphase flows have been developed, and among them some models have been commercialized. However, most of them have been developed based on a pressure-based approach; therefore, various numerical difficulties were involved inherently. Accordingly, in order to overcome these numerical difficulties, a multiphase flow model, MultiPhaSe flow (MPS), following a fractional-flow based approach was developed. In this study, by combining a contaminant transport module describing an enhanced dissolution effect of a surfactant with MPS, a MultiPhaSe flow and TranSport (MPSTS) model was developed. The developed model was verified using the analytical solution of Clement. The MPSTS model can simulate the process of surfactant enhanced aquifer remediation including interphase mass transfer and contaminant transport in multiphase flow by using the coupled particle tracking method and Lagrangian-Eulerian method. In this study, a surfactant was used in a non aqueous phase liquid (NAPL) contaminated area, and the effect of hydro-geological heterogeneity in the layered media on remediation efficiency was studied using the developed model. According to the numerical simulation, when hydraulic conductivity in a lower layer is 10 times, 20 times, and 50 times larger than that in an upper layer, the concentration of dissolved diesel in the lower layer is much higher than that in the upper layer because the surfactant moves faster along the lower layer owing to preferential flow; thus, the surfactant enhances dissolution of residual non aqueous phase liquid in the lower layer.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.104-111
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• 2019

Staged combustion cycle engines exhibit higher combustion performance compared with open cycle engines with a gas generator. An advanced research of the staged combustion cycle engine is going on for the next program following the KSLV-II program. Various experiments have been carried out for the technology demonstration model, TDM0A and TDM0B. The experiments on the combustion performance are aimed to understand the engine start condition and combustion characteristics. They also aim to develop the oxidizer-rich pre-burner and the combustor of the staged combustion cycle engine. The engine-shaped model, TDM1A is fabricated based on the experimental data. The combustion experiment of the TDM1A shows that the combustion pressure of the combustor is approximately 91 bar and the turbine rotation is approximately 28,00 rpm. The result is stable and satisfies the development requirements. The present paper reports on the development process and characteristics of engine models from TDM0A to TDM1A.

• Journal of Korea Water Resources Association
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• v.52 no.5
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• pp.313-323
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• 2019

Deep Tunnel system is a large-scale urban flood control facility installed underground in order to reinforce the lack of drainage systems in developed cities. In a structure like a deep tunnel system, the undular bore generated in the downstream causes a problem in the hydraulic stability of the tunnel. In this study, to investigate the influence of the undular bore on the hydraulic stability at the "Shinwol rainwater storage and drainage system", under construction for the first time in the country, a hydraulic model experiment was conducted on various flooding inflow scenarios. As a result of the hydraulic model experiment carried out in this study, the undular bore generated downstream is trapped in the pipe while moving to upstream, pushes the compressed air. It is judged that overflow occurred by choking the vertical drop shaft in the process when this compressed air is being exhaust through the upstream vertical drop shaft and blocking flood inflow. In addition, the analysis of velocity of undular bore shows that the undular bore transfers energy, and at this time, the pressure rose in the pipe and the velocity increment occurred of the undular bore. Further studies are needed to predict the size and velocity of undular bore, which plays an important role in the hydraulic stability of the tunnel in the deep tunnel system.

• Economic and Environmental Geology
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• v.54 no.6
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• pp.767-785
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• 2021

World-class magnesite deposits are developed in the Dashiqiao mineralized district of the Jiao-Liao-Ji Belt in China. This belt extends to the northern side of the Korean Peninsula and hosts major magnesite deposits in the Dancheon region of North Korea. Magnesite ores from the Pailou deposits in the Dashiqiao district is classified into pure magnetite, chlorite-magnetite, chlorite-talc-magnetite, and dolomite groups depending on the constituent minerals. According to the result of petrographic study, magnesite was formed by the alteration of dolomite, and, talc, chlorite, and apatite were produced as late-stage alteration minerals that replaced the magnesite. Fluid inclusions observed in magnesite are a liquid-type inclusion, with a homogenization temperature of 121-250 ℃ and a salinity of 1.7-22.4 wt% NaCl equiv. The chlorite geothermometer, indicating the temperature of hydrothermal alteration, is 137~293 ℃, slightly higher than the homogenization temperature of fluid inclusions, and the pressure is calculated to be less than 3.2 kb. For magnesite mineralization in the study area, the initially formed-dolomite was subjected to replacement by Mg-rich fluid to form a magnesite ore body, and then it was enriched through regional metamorphism and hydrothermal alteration. It seems that altered minerals such as talc were crystallized by Si and Al-rich late-stage hydrothermal fluids. These results are similar to the genetic environments of the Daeheung deposit, a representative magnesite deposit in North Korea, and it is believed that the two deposits went through a similar geological and ore genetic process of magnesite mineralization.

• Journal of Hospice and Palliative Care
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• v.24 no.4
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• pp.204-213
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• 2021

Purpose: At the end of life, communication is a key factor for good care. However, in clinical practice, it is difficult to adequately discuss end-of-life care. In order to understand and analyze how decision-making related to life-sustaining treatment (LST) is performed, the shared decision-making (SDM) behaviors of physicians were investigated. Methods: A questionnaire was designed after reviewing the literature on attitudes toward SDM or decision-making related to LST. A final item was added after consulting experts. The survey was completed by internal medicine residents and hematologists/medical oncologists who treat terminal cancer patients. Results: In total, 202 respondents completed the questionnaire, and 88.6% said that the decision to continue or end LST is usually a result of SDM since they believed that sufficient explanation is provided to patients and caregivers, patients and caregivers make their own decisions according to their values, and there is sufficient time for patients and caregivers to make a decision. Expected satisfaction with the decision-making process was the highest for caregivers (57.4%), followed by physicians (49.5%) and patients (41.1%). In total, 38.1% of respondents said that SDM was adequately practiced when making decisions related to LST. The most common reason for inadequate SDM was time pressure (89.6%). Conclusion: Although most physicians answered that they practiced SDM when making decisions regarding LST, satisfactory SDM is rarely practiced in the clinical field. A model for the proper implementation of SDM is needed, and additional studies must be conducted to develop an SDM model in collaboration with other academic organizations.

• Journal of the Korean Orthopaedic Association
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• v.56 no.4
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• pp.283-293
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• 2021

Degenerative disc disease has traditionally been thought of as low back pain caused by changes in the nucleus pulposus and annulus fibrous, in recent studies, however, changes in the upper and lower endplates cause degeneration of the disc, resulting in mechanical pressure, inflammatory reactions and low back pain. Recently, the bone marrow of the vertebral body-endplate-nucleus pulposus and annulus fibrous were considered as a single unit, and the relationship was explained. Once the endplate is damaged, it eventually aggravates the degeneration of the bone marrow, nucleus pulposus, and annulus fibrosus. In this process, the compression force of the annulus fibrosus increases, and an inflammatory reaction occurs due to inflammatory mediators. Hence, the sinuvertebral nerves and the basivertebral nerves are stimulated to cause back pain. If these changes become chronic, degenerative changes such as Modic changes occur in the bone marrow in the vertebrae. Finally, in the case of degenerative intervertebral disc disease, the bone marrow of the vertebral body-endplate-nucleus pulposus and annulus fibrous need to be considered as a single unit. Therefore, when treating patients with chronic low back pain, it is necessary to consider the changes in the nucleus pulposus and annulus fibrosus and a lesion of the endplate.

• 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.