• Journal of the Korean GEO-environmental Society
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• v.12 no.1
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• pp.61-70
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• 2011

The impact protection system consists of an arrangement of circular sheet pile cofferdams-denoted dolphin structuredeeply embedded in the seabed, filled with crushed rock and closed at the top with a robust concrete cap. Centrifuge model tests were performed to investigation the behaviors of dolphins in this study. Total 7 quasi-model tests and 11 dynamic model tests were performed. The main experimental results can be summarized as follows. Firstly, The experimental force-displacement results for quasi-static tests show a limited influence on the initial stiffness of the structure from the change in fill density and the related change in the stiffness of the fill. And by comparing the dissipation at the same dolphin displacement it was found that the denser fill increase the dissipation by 16% for the 20m dolphin and by 23% for the 30m dolphin. The larger sensitivity for the large dolphin is explained by a larger contribution to the dissipation from strain in the fill. In low level impacts the dynamic force-response is up to 26~58% larger than the quasi-static and the dissipation response is showed larger in small displacement. Hence, it is concluded conservative to use the quasi-static response characteristics in the approximation of the response, and it is further concluded that the dolphin resistance to low level impacts is demonstrated to be equivalent and even superior to the high level impacts.

• 한국사회정책
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• v.23 no.2
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• pp.141-172
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• 2016

This study examines the employment conditions and labour experience of elementary after-school care teachers in South Korea. Based on the empirical data collected through in-depth interviews with after-school care teachers in Gwangju Metropolitan City, the study considers multifaceted problems faced by after-school care teachers in their workplace. The after-school care class is part of educational policies initiated and rapidly expanded by the Ministry of Education, resulting in the substantial increase of non-regular school workers. The irregularization of after-school care teachers illustrates that the common problems faced by female non-regular workers, such as social discrimination, exclusion and inequality, are also transplanted into the typical public sector. In the case of Gwangju Metropolitan City, during the past two years there have been evident increases both in under 15-hour short time contract care teachers and outsourcing of care classes. Temporary part-time contract care teachers suffer relentless job insecurity and experience poor working conditions, exclusion and discrimination within the workplace and labour alienation. In order to minimize the organized resistance of care teachers, school authorities implicitly individualize and isolate care teachers through hierarchization, the division of labour and the spatial division of classes between indefinite and temporary contract teachers.

• Journal of the Korean Geotechnical Society
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• v.37 no.8
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• pp.5-13
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• 2021

Liquefaction behaviors of two natural silty samples containing fines including clay of 50% or more (Sample No.1 was silt 44.1% and clay 8.8%, sample No.2 was silt 57.2% and clay 12.4%) were examined by a cyclic triaxial test. According to the results on samples containing 50% or more of fine particles, an increase in the fine content decreases the liquefaction resistance of the sample. In other words, when the fine content increases, the liquefaction state of sample is reached with a small number of cyclic loads. In the relationship between the excess pore water pressure ratio and the number of cycles, the slope of the excess pore water pressure ratio increases more steeply as the fine content increases. As a result of analyzing the liquefaction behavior of the two silts with the content of clay contained in the fines, liquefaction occurred more easily in the No.2 silt with high clay content. This result shows that the clay contained in the fines affects the liquefaction behavior of the silt.

• Membrane Journal
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• v.31 no.6
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• pp.434-442
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• 2021

Poly(vinylidene fluoride) (PVDF) membrane has a good membrane durability because of its high mechanical resistance, thermal and chemical stability. However, the strong hydrophobic property of PVDF membrane can induce a low water permeability and easy fouling by proteins and organic matters. In order to improve the anti-fouling properties of PVDF membrane, the PVDF mixed matrix asymmetric membranes impregnated with biofunctional material 𝛽-cyclodextrin (𝛽-CD) in the membrane structure were prepared by phase inversion method. The membrane filtration experiments of pure water and BSA solution were performed using the PVDF/𝛽-CD mixed matrix asymmetric membranes prepared according to the 𝛽-CD contents. The experiments showed that the introduction of 𝛽-CD into the PVDF polymer matrix contributed to increase in the hydrophilic property of the PVDF membranes, and this led to the reduction of contact angles and improvement of anti-fouling properties. The PVDF/𝛽-CD membrane which was prepared using the dope solution with a 2 wt% 𝛽-CD content represented 64 L/m²·h of pure water flux, 95% of BSA rejection and maximum 80% of flux enhancements compared to flux results of the pristine PVDF membrane.

• Journal of the Korean Applied Science and Technology
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• v.39 no.1
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• pp.115-131
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• 2022

The purpose of this study was to develop and examine the effect of the Health Promotion Education Program for the Auxiliary Police based on the PRECEDE-PROCEED Model. This study was conducted using a nonequivalent control group pretest-posttest design. Twenty-five participants were selected by convenience sampling method and assigned to the experimental group, and 26 participants were assigned to the control group. The data were collected from Auxiliary Police officer in D provincial Police Agency. All of participations completed questionnaires about self-efficacy, social support, availability of resources, health promotion behavior, quality of life and received the objective stress test. In addition, the experimental group completed 7 sessions of health promotion Education programs according to PRECEDE-PROCEED model for 5 weeks. Data were analyzed using the SPSS/WIN 21.0 Program. There was significant differences over time between the groups in terms of health promotion behavior (F=7.63, p<.001), autonomic nervous activity (F=29.24, p<.001), stress resistance (F=31.22, p<.001), stress index (F=22.42, p<.001), fatigue (F=12.87, p<.001), and quality of life (F=3.49, p=.042). The results may be crucial to develop strategy in order to decrease the disease prevalence as well as increase the participants' overall quality of life. As a result, the Health Promotion Education Program for the auxiliary police was proved to be an effective intervention in order to improve the quality of life. Therefore, the program may be a useful intervention for the auxiliary police.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.3117-3129
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• 2022

Deeply understanding the phase change of thin liquid sodium film inside wick pore is very important for further studying high-temperature sodium heat pipe's heat transfer. For the first time, the evaporation and condensation of thin liquid sodium film are investigated by the Lennard-Jones potential of molecular dynamics. Based on the startup and normal operation of the sodium heat pipe, three different cases are simulated. First, the equilibrium is achieved and the Mass Accommodation Coefficients of the three cases are 0.3886, 0.2119, 0.2615 respectively. Secondly, the non-equilibrium is built. The change of liquid film thickness, the number of gas atoms, the net evaporation flux (J_net), the heat transfer coefficient (h) at the liquid-gas interface are acquired. Results indicate that the magnitude of the J_net and the h increase with the basic equilibrium temperature. In 520-600 K (the startup of the heat pipe), the h has approached 5-6 W m^-2 K^-1 while liquid film thickness is in 11-13 nm. The fact shows that during the initial startup of the sodium heat pipe, the thermal resistance at the liquid-gas interface can't be negligible. This work is the complement and extension for macroscopic investigation of heat transfer inside sodium heat pipe. It can provide a reference for further numerical simulation and optimal design of the sodium heat pipe in the future.

• Journal of the Korean Geotechnical Society
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• v.38 no.4
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• pp.47-58
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• 2022

Many 1g shaking table tests with an SDOF structure supported by a single pile were performed to evaluate the soil-structure interaction (SSI) effect. Since most structures supported by group piles are MDOF structures with columns, the SSI effect is simulated using a large 1g shaking table test and numerical analysis. According to the results, the movement in the piles tends to increase with input acceleration and when the input frequency is similar to the natural frequency. Furthermore, the slope of the dynamic p-y curve remains constant regardless of the variation of acceleration and input frequency. According to the results of the dynamic p-y backbone curve and the moment of group piles, a center pile with a leading pile has more soil resistance than side piles with a trailing pile, and the effect of group piles is observed above the 7D center to center pile distance.

• Journal of the Korean Society of Radiology
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• v.16 no.5
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• pp.649-660
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• 2022

In 1959, Satomura used spectral Doppler ultrasound to express the velocity of red blood cells according to time change, and Kato defined a zero-base line that could tell the direction of blood flow, making it possible to know the direction of blood flow. This became the basis for the widely used classifications of Triphasic, Biphasic, and Monophasic. However, the above classification has limitations that confuse users with the meaning and timing of use in a clinical environment. As a result, the American Society for Vascular Medicine (SVM) and the Society for Vascular Ultrasound (SVU) A consensus document on Doppler waveform analysis was declared by the joint committee. This study tried to review this consensus and to suggest nomenclature and modifiers that can be used in the domestic vascular ultrasound clinical field. The joint committee formed by SVM and SVU recommended that the use of the triphasic waveform and the biphasic waveform be used as a multiphasic waveform rather than being used due to the ambiguity of interpretation. In addition, it was agreed to name the hybrid-type waveform, which is a monophasic and high-resistance waveform, which has always been a problem of interpretation in a clinical environment, as an intermediate resistive waveform. In addition, in order to increase the communication efficiency between the interpreter and the sonographer, waveform analysis was classified into a main descriptor and a modifier, and it was recommended to use a single nomenclature by unifying various synonyms. It is expected that this literature review will provide accurate arterial spectral Doppler waveform interpretation and an agreed-upon nomenclature to radiologists performing vascular ultrasound examination in clinical practice, and will be utilized as basic data that can contribute to the improvement of public health.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.94-101
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• 2021

According to the Facility Management System (FMS) operated by the Korea Authority of Land & Infrastructure Safety, it is expected that the number of aging facilities that have been in use for more than 30 years will increase rapidly to 13.9% in 2019 and 34.5% in 2929, and end up with a social problem. In addition, with the revision of "Common Application of Seismic Design Criteria" by the Ministry of Public Administration and Security in 2017, it is mandatory to re-evaluate all existing road facilities and if necessary seismic reinforcement should be done to minimize the magnitude of earthquake damage and perform normal road functions. The seismic performance management-decision support technology currently used in seismic performance management practice in Korea only determines the earthquake-resistance reinforcement priority based on the qualitative index value for the seismic performance of individual facilities. However with this practice, normal traffic functions cannot be guaranteed. A new seismic performance management decision support technology that can provide various judgment data required for decision making is needed to overcome these shortcomings and better perform seismic performance management from a road network perspective.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.36-44
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• 2023

Core-shell TiO₂/Ag nanoparticles were synthesized by a modified sol-gel process and the reverse micelle method using acetoxime as a reducing agent in water/dodecylbenzenesulfonic acid (DDBA)/cyclohexane. The structure, shape, and size of the TiO₂/Ag nanoparticles were investigated using X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis (TGA). The size of TiO₂/Ag nanoparticles could be controlled by changing the [water]/[DDBA] molar ratio values. The size and the polydispersity of TiO₂/Ag nanoparticles increased when the [water]/[DDBA] molar ratio rose. The resultant Ag nanoparticles over the anatase crystal TiO₂ nanoparticles exhibited a strong surface plasmon resonance (SPR) peak at about 430 nm. The SPR peak shifted to the red side with the increase in nanoparticle size. Conductive pastes with 70 wt% TiO₂/Ag nanoparticles were prepared, and the pastes were coated on the PET films using a screen-printing method. The printed paste films of the TiO₂/Ag nanoparticles demonstrated greater surface resistance than conventional Ag paste in the range of 405~630 μΩ/sq.