• Journal of the Korean earth science society
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• v.37 no.4
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• pp.218-229
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• 2016

The bedform stability diagram indicates the shape and size of bedforms that will occur to a given grain size and flow velocity. The diagram has been constructed from experimental data which have been mostly acquired by flume experiments. Generally, the flume experiments have been performed on well sorted sediments with unimodal grain size distribution, in order to understand relationship between grain size and flow velocity. According to the diagram, a ripple structure initiates to be formed from lower flow regime flat bed, as the flow velocity increases on the surface of fine-sand or medium-sand sediments. This study aims to verify that the experimental result of bedform stability diagram will be reproduced in our flume experimental systems, and also to confirm that the result is consistent not only on well-sorted sand sediments but also on poorly-sorted sand sediments with bimodal grain size distribution. The experimental results in this study show that initiation of 2D or 3D ripple structure on poorly-sorted sand sediments requires higher flow velocity and shear stress than those for initiation of the structure on well-sorted sand sediments. In general, carbonate sediments are characterized by poor sorting due to inactive hydraulic sorting and bimodal grain size distribution with allochems and matrices. The results suggest that the carbonate depositional system possibly need a higher flow velocity for initial formation of 2D or 3D bedform structures. The reason might be the fact that pulling off and lifting of a grain in poorly sorted sediments require more energy due to sorting, friction, stabilization, armour effects, and their complex interaction. This preliminary study warrants additional experiments under various conditions and more accurate analysis on the relationship between formation of bedforms and grain size distribution.

• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.493-494
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• 2007

• Journal of the Korean earth science society
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• v.31 no.6
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• pp.608-624
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• 2010

Morphological surveys of southern Gyeonggi Bay in the Yellow Sea were conducted for2 years (2006 and 2007) by using multibeam echosounder for investigating the morphological features of bedforms. The subaqueous dunes are shown in various shapes (A~F type) and continuous spectrum of heights and lengths of transverse-to-current dunes on the wide range of sedimentary types. The height-length power-law correlation of dunes is $H_{mean}=0.0393L^{0.8984}$ (r=0.66). The comparison between Flemming (1988)'s correlation and height-length correlation of this study indicates that the subaqueous dunes in the study area are equilibrated in the present hydrological and sedimentary environment. The major controlling factors to thedevelopment and maintenance of subaqueous dunes are both strong tidal currents and the abundant availability of sand. Marine sand mining, artificial impact, changes from the original shape to an irregular shape of the subaqueous dunes with a shorter wavelength and lower height, which has influence on the development and maintenance of bedform because it causes a decrease of the availability of sediment. Water depth and sedimentary characteristics, and othercontrolling factors seem to play limited roles in the development and maintenance of subaqueous dunes.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.5-15
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• 2017

Three-hinge failure occurs in a jointed rock slope with a joint set parallel with slope and a conjugate joint set. Limit Equilibrium Method (LEM) and Finite Element Method (FEM) which are commonly used for slope design, are not suitable for evaluating stability against three-hinge failure, and this study performed parametric study to analyze the failure mechanism and to find influence factors causing three-hinge failure using UDEC which is a commercial two-dimensional DEM based numerical program. Numerical analyses were performed for various joint structural conditions and joint properties as well as ground water conditions. It was found that pore water pressure is the main factor triggering the three-hinge failure and the mode of failure depends on friction angle of basal joint and bedding joint set. The results obtained from this study can be used for adequate and economic footwall slope reinforcement design and construction.

• The Journal of Engineering Geology
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• v.1 no.1
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• pp.121-136
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• 1991

The focal mechanism of the Hongsung Earthquake (1978. Oct. 7, M$_L$=5.0, Latitude 36.62N, Longitude 1 26.67E) was evaulated using the polarity distribution of the P-Waveforms. Through the non-linear computer process, the compatibility of polarity distributions of the 9 P-Waveforms observed at teleseismic distances from the Hongsung Earthquake epicenter was investigated to those of the focal mechanism determined from the varying strike, dip and rake angles. The resultant values for the strike and dip angle of the principal fault plane, which apparently matches very well the sunface lineament of the Hongsung region, are determined to be about 247 degree and 78 degree with uncertainties, respectively. However, the rake angle of the focal mechanism has wide range of 40 degree to 160 degree, which is mainly due to the poor coverage of the azimuthal angle of the observed seismic stations. Due to the consistency of principal stress axes, the resultant focal mechanism could support the current stress regime of that region, which may be caused by subduction of the Pacific Plate under the Eurasia Plate along the Japan Trench. It also provides information of seismic source characteristics of the part of the Korean Peninsula for aseismic design criteria such as Site Specific Response Spectrum and Strong Ground Motion Time History for the nuclear power plants and related nuclear waste disposal facility sites.

• Journal of the Korean association of regional geographers
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• v.22 no.3
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• pp.681-702
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• 2016

Two different modelling approaches to dune dynamics have been established thus far; continuous models that emphasize the precise representation of wind field, and feedback-based models that focus on the interactions between dunes, rather than aerodynamics. Though feedback-based models have proven their capability to capture the essence of dune dynamics, the compatibility issues on these models have less been addressed. This research investigated, mostly from the theoretical point of view, the algorithmic compatibility of three feedback-based dune models: sand slab models, Nishimori model, and de Castro model. Major findings are as follows. First, sand slab models and de Castro model are both compatible in terms of flux perspectives, whereas Nishimori model needs a tuning factor. Second, the algorithm of avalanching can be easily implemented via repetitive spatial smoothing, showing high compatibility between models. Finally, the wind shadow rule might not be a necessary component to reproduce dune patterns unlike the interpretation or assumption of previous studies. The wind shadow rule, rather, might be more important in understanding bedform-level interactions. Overall, three models show high compatibility between them, or seem to require relatively small modification, though more thorough investigation is needed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.659-665
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• 2016

The limit equilibrium method (LEM) is commonly used for slope design and stability analysis because it is easy to simulate slope and requires short calculating time. However, LEM cannot adequately simulate ploughing failure in a footwall slope with a joint set dipping parallel with slope, e.g. bedding joint set. This study performed parametric study to analyze the influence factors on ploughing failure using UDEC which is a commercial two-dimensional DEM (Distinct Element Method)-based numerical program. The influence of joint structure and properties on stability of a footwall slope against ploughing failure was investigated, and the factor of safety was estimated using the shear strength reduction method. It was found that the stability of footwall slope against ploughing failure strongly relies on dip angle of conjugate joint, and the critical bedding joint spacing and the critical length of slab triggering ploughing failure are also affected by dip angle of conjugate joint. The results obtained from this study can be used for effective slope design and construction including reinforcement.

• Journal of Korea Entertainment Industry Association
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• v.13 no.4
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• pp.131-138
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• 2019

The film enters the color film from black and white, and the screen image changes qualitatively. The color in the film not only has the reproduction function of the restoration object like the objective appearance, but also has the function of conveying different subjective emotions. It can express the color and can't express it. The artistic effect conveys the information content that the story itself can't convey, so the color of the film becomes an important part of the film language. The color in the film is presented on the screen in the form of single-screen color, scene color, full-color color tone, and various color chains designed according to different contradictions and conflicts. Because the film art and art means are assembled by montage, he colors in the picture also form a montage form. People call it "color montage". People's subjective nature of color criticism and acceptance of color language also depend on various local tones. The accurate expression of the relationship, the unique attribute of color determines that the color must enter the structural state in order to express its unique charm. The color of the film only has the real aesthetic value when it enters the level of "color structure". This paper studies the color of Chinese and Western films from the differences between the color thinking of Chinese and Western film directors and the cultural implication of Chinese and Western film colors. The western film director emphasizes the structure of color and pays attention to the use of tonal montage to convey the characters. Emotions reflect the characteristics of a subjective color. Beginning with the "fifth-generation" director of Chinese film, the new journey of film color language has been opened. In the process of blending love and scenery, the film style of "image-in-one" has been achieved.

• Journal of the Geological Society of Korea
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• v.54 no.5
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• pp.477-488
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• 2018

Fluid muds commonly occur in estuarine environments, but their ancient examples have rarely been studied in terms of depositional characteristics and processes. Cores of estuarine channel deposits of the Early Cretaceous McMurray Formation, Alberta, Canada show various mudstone layers that possess depositional characteristics of high clay-concentration flows. These mudstone layers are examined in detail through microscopic observation of thin sections and classified into three microfacies (<1 to 25 mm thick) on the basis of sedimentary texture and structures. Structureless mudstone (Microfacies 1) consists mainly of clay particles and contains randomly dispersed coarser grains (coarse silt to fine sand). This microfacies is interpreted as being deposited by cohesive mud flows, i.e., fluid muds, which possessed sufficient strength to support suspended coarser grains (quasi-laminar plug flow). Silt-streaked mudstone (Microfacies 2) mainly comprises mudstone with dispersed coarse grains and includes very thin, discontinuous silt streaks of coarse-silt to very-fine-sand grains. The texture similar to Microfacies 1 indicates that Microfacies 2 was also deposited by cohesive fluid muds. The silt streaks are, however, suggestive of the presence of intermittent weak turbulence under the plug (upper transitional plug flow). Heterolithic laminated mudstone (Microfacies 3) is characterized by alternation of relatively thick silt laminae and much thinner clay laminae. It is either parallel-laminated or low-angle cross-laminated, occasionally showing low-amplitude ripple forms. The heterolithic laminae are interpreted as the results of shear sorting in the basal turbulent zone under a cohesive plug. They may represent low-amplitude bed-waves formed under lower transitional plug flows. These three microfacies reflect a range of flow phases of fluid muds, which change with flow velocities and suspended mud concentrations. The results of this study provide important knowledge to recognize fluid-mud deposits in ancient sequences and to better understand depositional processes of mudstones.