• International Area Studies Review
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• v.18 no.3
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• pp.249-265
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• 2014

The international mobile roaming service has been provided for more than one decade, but high price of international mobile roaming service, which is represented as 'bill shock' is still of major concern in lots of countries including Korea. With understanding of the given price issues, the international organizations, such as OECD, EU, WTO, ITU have been conducting extensive analyses and studies to find suitable solutions and appropriate measures. In the case of EU regulate the international roaming charges and implement the regulation policy. OECD do not have a compelling regulation on roaming charges, but OECD request to member state to find the reasons of high roaming charges and its solution. WTO Council for Trade in Services is reviewing the international mobile roaming in terms of whether impede international trade in services. The purpose of this study is to review many different approaches in international organizations related to reducing international roaming service charges, to drive some regulatory policy directions for reducing roaming charges.

• Membrane Journal
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• v.29 no.1
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• pp.61-65
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• 2019

Anisotropic particles have been issued in various fields due to their unique physical properties. Herein, a novel dynamic phase separation method (DPS) is introduced to fabricate anisotropic acorn-like nanoparticles. DPS consists of two dynamic conditions; solvent evaporation and nonsolvent induced precipitation. The bottom layer is controlled by feeding the water as a non-solvent diluent, and the phase separation of the upper layer relies on the diffusion and evaporation of a volatile good solvent. At this condition, the acorn-like particles were fabricated. Under a closed box filled with water (spontaneous phase separation), monodisperse polystyrene (PS) particles were synthesized. At the coexistence between DPS and spontaneous phase separation, the sizes of cap and particle were changed. Also, the volume of PS solutions influences on the particle shape. Since the unique structures could be utilized into various applications, if advanced techniques such as membrane-based controlled water feeding is developed, monodisperse acorn-like particles could be tuned.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.474-481
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• 2018

This paper is to compare by numerical analysis the flow characteristics and propulsion performance of stern with the shape change of K-duct, a pre-swirl duct developed by Korea Research Institute of Ships & Ocean Engineering (KRISO). First, the characteristics of the propeller and the resistance and self-propulsion before and after the attachment of the K-duct to the ship were verified and the validity of the calculation method was confirmed by comparing this result with the model test results. After that, resistance and self-propulsion calculations were performed by the same numerical method when the K-duct was changed into five different shapes. The efficiency of the other five cases was compared using the delivery horsepower in the model scale and the flow characteristics of the stern were analyzed as the velocity and pressure distributions in the area between the duct end and the propeller plane. For the computation, STAR-CCM +, a general-purpose flow analysis program, was used and the Reynolds Averaged Navier-Stokes (RANS) equations were applied. Rigid Body Motion (RBM) method was used for the propeller rotating motion and SST $k-{\omega}$ turbulence model was applied for the turbulence model. As a result, the tangential velocity of the propeller inflow changed according to the position angle change of the stator, and the pressure of the propeller hub and the cap changes. This regulated the propeller hub vortex. It was confirmed that the vortex of the portion where the fixed blade and the duct meet was reduced by blunt change.

• Herbal Formula Science
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• v.27 no.3
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• pp.213-221
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• 2019

Objectives : The purpose of this study is to confirm the efficacy and safety of the treatment of gastritis with 'Hwangryunhaedok-tang'. Methods : Total 20 people, between 19 and 65 years old, will be recruited to participate in a comparative clinical trial. All subjects will take 2 capsules of Hwangryunhaedok-tang (Redoxin Cap.), 3 times a day, 30 minutes after meals, for 8 weeks. Outcomes will be measured at the baseline, 4th week, and 8th week. Primary outcomes is the improvement rates of gastritis symptoms, such as heartburn, nausea/vomiting, abdominal bloating, anorexia, heartburn, and trim. Results : This trial was approved by institutional review board of Pusan National University Korean Medicine Hospital (registry number: 2018011), and registered in Clinical Research information Service, one of WHO. Recruitment opened in April 2019 and is supposed to be completed by December 2019. Conclusions : This trial will provide clinical information to determine the efficacy and safety of treatment of gastritis with 'Hwangryunhaedok-tang'.

• International Area Studies Review
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• v.16 no.3
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• pp.323-341
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• 2012

In the recent year, the urbanization is emerging as important issue for sustainable development in China. Like the most of the world, urbanization of China is closely related with the domestic market development, the innovation of industrial structure, and the reduction of income cap among regions, urban-rural region and so on. This paper analyzes the impact of urbanization on economic growth using cross section data and time series data of the eastern coastal regions in China. Based on the existing literature, we establish a hypothesis, which is basically the same as Williamson(1965)'s hypothesis, that urbanization promotes the economic growth at the early stages of development but has adverse effects in economies that have reached a certain income level. The results of study are as follows: Using 10-provinces data of the eastern coastal region in China, this paper examines the impact of urbanization on economic growth. Regression results suggest that Williamson's hypothesis is not verified, regardless of estimation methods in two models. Hence, the results show that the impact of urbanization on economic growth has not the inverse U-type function in the eastern coastal region of China.

• Journal of the Korea Fashion and Costume Design Association
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• v.20 no.4
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• pp.41-56
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• 2018

The purposes of this study were to investigate preference of Baekje culture relics and to examine purchasing behaviors of fashion cultural products of adolescents. The subjects were 421 adolescents and measuring instruments consisted of Baekje relics preference items, fashion cultural products purchasing behaviors items, and subject' demographic attributions. The data were analyzed by frequency analysis, $x^2$ test, factor analysis, t-test, ANOVA and Duncan's multiple range test using SPSS program. The results were as follows. First, adolescents were more likely to prefer crown ornaments of the King Muryong in Kongju region, and gilt-bronze incense burner and halo in Buyeo region. Second, as fashion cultural products, adolescents were more likely to prefer T-shirts and accessory items, and modern image. As product selection criteria, they considered aesthetics as the most important factor, followed by symbolism and practicality. Adolescents evaluated the resonable purchase price of fashion cultural products as less than 20,000 won for T-shirts, cap & bag, and less than 10,000 won for accessories. The adolescent's satisfaction of fashion cultural products was low, and the main dissatisfaction was high prices, and the lack of practicality and diversity. Third, the preference for Baekje cultural relics and purchasing behaviors of fashion cultural products differed according to age and sex of adolescents. This study showed that fashion culture products for adolescents need to be designed in a modern sense with a unique cultural symbolism, focusing on T-shirts and accessories items. In addition, fashion cultural products companies should established the product development plan considering the characteristics according to the age and sex of adolescents.

• Geomechanics and Engineering
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• v.16 no.6
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• pp.589-597
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• 2018

Centrifuge model tests were used to simulate pile-raft composite foundation and pile-geogrid composite foundation with different pile spacing for researching the time effect of negative skin friction of rigid piles in high-speed railways. The research results show that the negative skin friction has a significant impact on the bearing capacity of composite foundation. Pile-raft composite foundation has higher bearing capacity compared to pile-geogrid composite foundation to reduce the effect of negative skin friction on piles. Both the foundation settlement and negative skin friction have significant time effect. The distribution of skin friction can be simplified as a triangle along the pile. The neutral point position moves deeper in the postconstruction stage at larger pile spacing. For pile-geogrid composite foundation, the setting of pile-cap affects the position of neutral point in the post-construction stage. Reinforced cushion with geotextile may promote the better performance of cushion for transmitting the loads to piles and surrounding soils. Arching effect in the cushion of the composite foundation is a progressive process. The compression of the rigid piles contributes less than 20% to 25% of the total settlement while the penetration of the piles and the compression of the bearing stratum below the pile tips contribute more than 70% of the total settlement. Some effective measures to reduce the settlement of soils need to be taken into consideration to improve the bearing capacity of pile foundation.

• Current Applied Physics
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• v.18 no.11
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• pp.1338-1344
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• 2018

Band parameters and superconductivity of yttrium hypocarbide ($Y_2C$) have been investigated. The computations are performed using first-principles pseudopotential method within a generalized gradient approximation. The equilibrium lattice parameters have been determined and compared with experiment. Moreover, the material of interest is found to be stiffer for strains along the a-axis than those along the c-axis. A band-structure analysis of $Y_2C$ implied that the latter has a metallic character. The examination of Eliashberg Spectral Function indicates that Y-related phonon modes as well as C-related phonon modes are considerably involved in the progress of scattering of electrons. By integrating this function, the value of the average electron-phonon coupling parameter (${\lambda}$) is found to be 0.362 suggesting thus that $Y_2C$ is a weak coupling Bardeen-Copper-Schrieffer superconductor. The use of a reasonable value for the effective Coulomb repulsion parameter (${\mu}^*=0.10$) yielded a superconducting critical temperature $T_c$ of 0.59 K which is comparable with a previous theoretical value of 0.33 K. Upon compression (at pressure of 10 GPa) ${\lambda}$ and $T_c$ are increased to be 0.366 and 0.89 K, respectively, showing thus the pressure effect on the superconductivity in $Y_2C$. The spin-polarization calculations showed that the difference in the total energy between the magnetic and non-magnetic $Y_2C$ is weak.

• Current Applied Physics
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• v.18 no.12
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• pp.1473-1479
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• 2018

Recently multiferroic materials have attract great interest for the applications on memorial, spintronic and magneto-electric sensor devices for their spontaneous magneto-electric coupling properties. Research and development of the various kinds of multiferroics are indispensable factor for a new generation multifunctional materials. In this research, mechanical, electronic, magnetic and nonlinear optical properties of La modified $BiLaFe_2O_6$ (BLFO) and Mn modified $Bi_2FeMnO_6$ (BFMO) were studied as new members of multiferroic $BiFeO_3$ (BFO) series by first-principles calculations, and compared with the pure BFO to discover the optimized properties. Our results show that BLFO and BFMO have good mechanical stability as revealed by elastic constants that satisfy the stability criteria. All these compounds exhibit anisotropic and ductile nature. The enhanced properties by La and Mn substitution, such as increased hardness, improved magnetism, decreased band gap and comparable second harmonic generation responses reveal that the new multiferroic members of BLFO and BFMO would get wider application than their BFO counterpart. Our study is expected to providing an appropriate mechanical reference data as guidance for engineering of high efficiency multifunctional devices with the BFO series.

• Current Applied Physics
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• v.18 no.12
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• pp.1577-1582
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• 2018

While controlling the cation contents in perovskite rare-earth nickelate thin films, a metal-to-insulator phase transition is reported. Systematic control of cation stoichiometry has been achieved by manipulating the irradiation of excimer laser in pulsed laser deposition. Two rare-earth nickelate bilayer thin-film heterostructures with the controlled cation stoichiometry (i.e. stoichiometric and Ni-excessive) have been fabricated. It is found that the Ni-excessive nickelate film is structurally less dense than the stoichiometric film, albeit both of them are epitaxial and coherent with respect to the underlying substrate. More interestingly, as a temperature decreases, a metal-to-insulator transition is only observed in the Ni-excessive nickelate films, which can be associated with the enhanced disproportionation of the Ni charge valence. Based on our theoretical results, possible origins (e.g. anti-site defects) of the low-temperature insulating state are discussed with the need of future work for deeper understanding. Our work can be utilized to realize unusual physical phenomena (e.g. metal-to-insulator phase transitions) in complex oxide films by manipulating the chemical stoichiometry in pulsed laser deposition.