• Journal of Korea Water Resources Association
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• v.44 no.1
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• pp.41-49
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• 2011

This study is a research based on an existing analysis that peak values of unit hydrograph are variant according to rainfall intensity in a watershed. Differently from the fundamental assumption that an unit hydrograph is time-invariant in a watershed a variant unit hydrograph to rainfall intensity by storms is defined and applied into rainfall events, which produces out runoff hydrograph for an examination. Peak flow and time to peak of unit hydrograph used for an application are obtained from the relation equation with rainfall intensity developed by a previous study reviewed, and its shape is made by Nash unit hydrograph which is determined by the peak values. For the purpose of a comparison an invariant unit hydrograph is defined as Nash model obtained from averaged peak values of unit hydrograph which is derived by 26 rainfall storms. Peak flow and time to peak of flood hydrograph developed respectively by variant unit hydrograph with rainfall intensity and an averaged unit hydrograph are compared to those of the observed hydrograph. With comparing both hydrographs calculated by averaged unit hydrograph and revised unit hydrograph to observed hydrograph it is shown the peak flow and time to peak of hydrograph calculated by time-invariant unit hydrograph revised in this study are closer to those of observed hydrograph than those calculated by averaged unit hydrograph.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.3
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• pp.180-188
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• 1999

The dynamic elastic properties of metal matrix composites were investigated by resonant ultrasound spectroscopy(RUS). The composites used in this study consisted of 2124 aluminum alloy reinforced with different concentrations of SiC particles. RUS can determine the nine independent elastic stiffness($C_{ij}$) for the orthorhombic symmetry on a small specimen simultaneously. The elastic constants were determined as a function of the volume fraction. A concept of effective aspect ratio. which combine the aspect ratio and the orientation of reinforcement. was used to calculate the initial moduli from Mori-Tanaka theory for the input of RUS minimization code. Young's moduli can be obtained from the measured stiffnesses. The results show that the elastic stiffness increases with increment of the particle content. The behavior of elastic stiffness indicates that the particle redistribution induced by the extrusion process enlarges the transversely isotropic symmetry as the fraction of reinforced particles increase. This relationship could be used for determination of the volume fractions of reinforcement as a potential tool of nondestructive material characterization.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.141-155
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• 2018

Recently, the number of ground subsidence resulting from underground cavity has been increased. Accordingly, the importance of restoration of stress release zone around the underground cavity has been emphasized. The stress release zone is composed of low density soils having extremely low stiffness and degree of compaction, which can lead to additional cavity expansion and collapse of overlying ground. Therefore, in this study, the suitability of restoration method of underground cavity using expansive material for reinforcement of stress release zone around the cavity is verified. The basic physical properties and expansion characteristics of the expansive material were examined. The experiment equipment capable simulating of stress release zone was developed and is used to investigate the effect of expanding material on stress release zone. The stress release zone was simulated using the spring in numerical analysis. The factors of the volume ratio of the underground cavity to the expansion material, the degree of stress relaxation, and the shape of the cavity were varied in numerical simulations, and the behavior of stress release zone was analyzed based on the numerical analysis results. Analysis variables are factors that affect each other. Also, filling of underground cavity and capacity of restoration of stress release zone were confirmed when the expansive material was inserted into underground cavity.

• Journal of the Korean Electrochemical Society
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• v.22 no.3
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• pp.87-103
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• 2019

Nonaqueous organic electrolyte solution in commercially available lithium-ion batteries, due to its flammability, corrosiveness, high volatility, and thermal instability, is demanding to be substituted by safer solid electrolyte with higher cycle stability, which will be utilized effectively in large-scale power sources such as electric vehicles and energy storage system. Of various types of solid electrolytes, composite solid electrolytes with polymer matrix and active inorganic fillers are now most promising in achieving higher ionic conductivity and excellent interface contact. In this review, some kinds and brief history of solid electrolyte are at first introduced and consequent explanations of polymer solid electrolytes and inorganic solid electrolytes (including active and inactive fillers) are comprehensively carried out. Composite solid electrolytes including these polymer and inorganic materials are also described with their electrochemical properties in terms of filler shapes, such as particle (0D), fiber (1D), plane (2D), and solid body (3D). In particular, in all-solid-state lithium batteries using lithium metal anode, the interface characteristics are discussed in terms of cathode-electrolyte interface, anode-electrolyte interface, and interparticle interface. Finally, current requisites and future perspectives for the composite solid electrolytes are suggested by help of some decent reviews recently reported.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.29-36
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• 2019

This study investigated the self-healing properties of blast furnace slag cement paste sample with $Na_2SO_4$ as a blast furnace slag activator after conducting the permeability test. Self-healing properties were examined by crack filling ratio and quantification of self-healing products. The degree of self-healing was evaluated by the crack filling ratio, and the crack filling ratio was analyzed by panoramic analysis using BSE-DIP for objectivity. The average crack filling ratio showed a tendency of decreasing from the upper part of the specimen to the lower part as the average of the top part was 18%, the middle part was 7% and the bottom part was 5% on average. The maximum crack filling ratio was 44% and the minimum crack filling ratio was 3%. The residual self-healing product after the permeability test contained a large amount of Ca element and Al element derived from the blast furnace slag, and the Si element was mainly present near the crack surface. The most abundant minerals in self-healing products were about 68% C-A-H. $CaCO_3$ was about 13% and C-A-S-H was about 8%. Three minerals accounted for 90% of self-healing products. C-A-H was mainly present at a part slightly distant from the crack surface and showed an angular or acicular shape. The C-A-S-H was generated on the surface naturally connected to the existing specimen, and the $CaCO_3$ was generally observed on the surface of the specimen or the inside of the crack.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.313-320
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• 2018

The purposes of this study were to verify the status of Barrier Free Design Certification in the center for the elderly. To achieve these purposes, the architectural characteristics of the center for elderly and the status of Barrier Free Design Certification was analyzed. The results of this study were as follows. (1) The functional composition of centers for the elderly are similar regardless of the location, but the area and shape of the plot are very different according to the location. (2) According to an analysis on the status of Barrier Free Design Certification in centers for elderly, the sanitation and intermediate facilities are necessarily considerable adjustment. (3) For the accessability and conveniences of Barrier Free Design Certification in a small building, such as centers for the elderly, they are necessary to simplify the self-assessment documents, minimize the period for judging, and reducing the fees for certification.

• (The)Study of the Eastern Classic
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• no.68
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• pp.409-437
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• 2017

The curiosity of the human afterlife created many imaginations. The Death Angel's Character are also the product of this imagination. This is because we needed a connection between this world and the otherworld in human' imaginations. The Death Angel revealed in detail in Shamanistic Epics. First, It is the person who performs the task assigned by The King of the Otherworld. Second, It is a person who can go to this world and the otherworld. Third, It is the person who takes the deceased to the otherworld. Fourth, It is the person who takes out the soul of human and modify the life list. Fifth, It is the person who sympathetic and humane qualities. This The Death Angel's character is actively accepted in modern contents. The most representative works are <49 Days>, , . Contemporary content, but the otherworld and the afterlife were accepted. And The Death Angel played an important role. Of course, this process also happens that modern changes. Namely, Function and personality retains existing character. And the appearance and background change a modern sense. As a result, The Death Angel became a new character through the encounter between the past and the present.

• Conservation Science in Museum
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• v.26
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• pp.83-182
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• 2021

This study summarized the results of the conservation treatment and investigation on the production method of the golden crown (Treasure No. 339) excavated from Tomb No. 129 (also known as Seobongchong Tomb) in Noseo-dong, Gyeongju-si, Gyeongsangbuk-do Province. The golden crown from Seobongchong Tomb was discovered during the excavations conducted by the Museum of the Government-General of Korea in 1926 during the Japanese colonial era. It is currently in the collection of the National Museum of Korea. A total of six Silla golden crowns have survived in Korea, among which the crown from Seobongchong Tomb is the only example with a dome-shaped hemispherical decoration attached with a bird ornament while otherwise showing the typical features of Silla crowns. The crown had been repaired following its excavation using metallic materials and adhesives, but due to the partial deformation and damage brought about by the repair materials, it required further conservation treatment. This article describes in detail the overall process of the conservation treatment and the restoration of the original form of the golden crown from Seobongchong Tomb, particularly the method of reinforcing the joints to secure the stability of the crown. It presents the characteristics of the crown's production as revealed in the investigation during the conservation treatment, and further analyzes the relationship of this crown from Seobongchong Tomb with other Silla crowns through a comparison of their production techniques. The investigation revealed that the crown was primarily decorated with golden sequins at the time of its production. At a later point some of the sequins in the upright ornament were replaced with comma-shaped jade beads and additional comma-shaped jade beads were added to the headband. In order to determine if such modifications to the decoration had occurred with other Silla crowns, the decoration of the six extant Silla golden crowns were investigated. The crown from Cheonmachong Tomb features traces of this same modification to the decoration and possesses other similarities with the crown from Seobongchong Tomb.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.5
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• pp.617-626
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• 2022

In Korea, annual precipitation and its variability have gradually increased since modern meteorological observations began, and the risk of disasters has also been increasing due to significant regional variations and recent abnormal climate conditions. Given that damage from storms and floods mainly occurs around rivers, it is crucial to determine the appropriate design frequency for river-related projects. This study examined existing design practices used to determine hydrological design frequencies and suggested a new method to determine appropriate design frequencies. The study collected available data pertaining to seven evaluation factors, specifically the basin areas, shape parameters, channel slopes, stream orders, backwater effect reaches, extreme rainfall frequencies, and urbanized flood inundation areasfor 413 local rivers in Chungcheongnam-do in Korea. The estimated weights for areas of extreme rainfall frequencies and urbanized flood inundation were found to be 18, having a great effect on determining the design frequency. Compared with the established design frequency in previous government reports, the estimated design frequency increased for 255 rivers and decreased for 158 rivers.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1222-1230
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• 2022

The rotor blade is an important component of a tidal stream turbine and is affected by a large thrust force and load due to the high density of seawater. Therefore, the performance must be secured through the geometrical and structural design of the blade and the blade structural safety to which the composite material is applied. In this study, a 1 MW class large turbine blade was designed using the blade element momentum (BEM) theory. GFRP is a fiber-reinforced plastic used for turbine blade materials. A sandwich structure was applied with CFRP to lay-up the blade cross-section. In addition, to evaluate structural safety according to flow variations, static load analysis within the linear elasticity range was performed using the fluid-structure interactive (FSI) method. Structural safety was evaluated by analyzing tip deflection, strain, and failure index of the blade due to bending moment. As a result, Model-B was able to reduce blade tip deflection and weight. In addition, safety could be secured by indicating that the failure index, inverse reserve factor (IRF), was 1 or less in all load ranges excluding 3.0*Vr of Model-A. In the future, structural safety will be evaluated by applying various failure theories and redesigning the laminated pattern as well as the change of blade material.