• The Journal of the Convergence on Culture Technology
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• v.5 no.3
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• pp.345-349
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• 2019

In Korea, the mountainous area occupies more than 70% of the whole country, cutting of earth slope that cuts a part of the ground surface is widely used when building infrastructures such as road, railroad, and industrial complex construction. In recent years, regulations on environmental damage have become more strict, and various methods have been developed and applied. Among them, Concrete-Panel Retaining Wall technique is actively applied. Concrete-Panel Retaining Wall is a method to resist horizontal earth pressure by forming a wall by attaching a precast retaining wall to the front of the support material and increasing the shear strength of the disk through reinforcement of the support material. Soil nailing, earth bolt, and ground anchor are used as support material. Among them, ground anchor is a more aggressive reinforcement type that introduces tensile load in advance to the steel wire, and a large concentrated load acts on the front panel. This concentrated load is a factor that creates cracks in the concrete panel and reduces the durability of the retaining wall itself. In this study, steel pipe sleeves and reinforcements were purchased at the anchorage of the panel to prevent cracks, and by applying bumpy shear keys to the end of the panel, the weakness of the individual behavior of the existing grout anchors was improved. The problem of degraded landscape by exposure to front concrete of retaining wall and protrusion of anchorage was solved by the production of natural stone patterns and the construction of sections that do not protrude the anchorage. In order to verify the effectiveness of anti-crack sleeves and reinforcements used in the null, indoor testing and three-dimensional numerical analysis have been performed, and the use of steel pipe sleeves and reinforcements has demonstrated the overall strength increase and crack suppression effect of panels.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.116-122
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• 2021

This study quantitatively evaluated the performance improvement of a circular reinforced concrete pier under dynamic load with strengthening using a steel plate. Various three-dimensional elements were applied using the finite element program ABAQUS. The analytical parameters included the ratios of the steel cover length to the pier's total height and the ratios of the steel cover thickness to the pier diameter for inelastic-nonlinear analysis. The lower part of the pier had fixed boundary conditions, and lateral repetitive loads were applied at the top of the pier. The pier was investigated to evaluate the dynamic performance based on the load-displacement curve, stress-strain curve, ductility, energy absorption capability, and energy ratio. The yield and ultimate loads of piers with steel covers increased by 3.76 times, and the energy absorption capability increased by 4 times due to the confinement effects caused by the steel plate. A plastic hinge part of the column with a steel plate improved the ductility, and the thicker the steel plate was, the greater the energy absorption capacity. This study shows that the reinforced pier should be improved in terms of the seismic performance.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.2
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• pp.153-167
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• 2005

The purpose of this study was to compare the v-shape thread with the square shape thread of fixture in the view of stress distribution pattern using finite element stress analysis. The finite element model was designed with the parallel placement of two standard fixtures(4.0 mm diameter ${\times}$ 11.5 mm length) on the region of mandibular 1st and 2nd molars. Three dimensional finite element model was created with the components of the implant and surrounding bone. This study simulated loads of 200 N at the central fossa in a axial direction (load A), 200 N at the buccal offset load that is 2 mm apart from central fossa in a axial direction (load B), 200 N at the buccal offset load that was 4 mm apart from central fossa in a axial direction (load C). These forces of load A',B',C' were applied to a $15^{\circ}$ inward oblique direction at that same site with 200 N. Von Mises stress values were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study : 1. The highest stress concentration occurred at the cervical region of the implant fixture. 2. Von Mises stress value of off-site region was higher than that of central fossa region. 3. Square shape thread type showed more even stress distribution in the vertical and oblique force than V-shape thread type. 4. Stress distribution was the most effective in the case of buccal offset load (2, 4 mm distance from central fossa) in the square shape thread type. 5. V-shape thread type revealed higher von Mises stress value than square shape thread type in all environmental condition. The results from numerical analyses concluded that square shape thread type had the lower destructive stress and more stress distribution between the fixture and bone interface than V-shape thread type. Therefore, square shape thread type was regarded as optimal thread configuration in biomechanical concepts.

• The Journal of Engineering Geology
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• v.27 no.1
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• pp.81-90
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• 2017

Preceding displacements in tunnel are difficult to predict since the measurements of displacements after excavation can not be performed immediately. In the present study, The longitudinal displacements which can be measured immediately after excavation are used to predict the crown settlements occurring before excavation only if fault is located at the tunnel crown. Three-dimensional finite element analysis was conducted using 28 numerical models with various fault attitudes to analyze the correlation between the longitudinal displacements on tunnel face and preceding crown settlements. The results, $L_{face}/C$ ratio show 2~12% in the drives with dip models and 2~13% in the drives against dip models individually. In addition, each model has a certain $L_{face}/C$ ratio. The result of the regression analysis show that the coefficient of determination is over 0.8 in most models. Therefore, crown settlements occurring before excavation can be predicted by analyzing the longitudinal displacements occurring on tunnel faces.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.3
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• pp.121-129
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• 2004

The different types of coastal souctures have been constructed for the protection of coastal region from the incident waves. Among them. the permeable submerged breakwater has been widely used as a wave dissipater and sediment transport controller because of its excellent advantages in scenery effects, construction efficiency and environment aspects. This study numerically investigated the characteristics of wave energy variations and transmission coefficient at the rear of the permeable submerged breakwater installed in the irregular wave field. To analyze it's performance numerically, a two-dimensional numerical wave flume based on VOF method was used. A frequency spectral analysis showed that the spectral peak moved to the short-period in the one-row submerged breakwater, and the wave energy was distributed evenly for the whole period in the two-row submerged breakwater in the case of breaking on the submerged breakwater. The spectral peak was shown to be converged within the significant wave period at the rear of the permeable submerged breakwater in the case of non-breaking conditions. From the result of transmission coefficients analysis. it was confirmed that a considerable quantity of wave energy was transmitted to the rear of the permeable submerged breakwater in the case of non-breaking rather than breaking.

• Tunnel and Underground Space
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• v.14 no.3
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• pp.215-228
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• 2004

Rock mass contains discontinuities such as faults and joints, and their mechanical properties and spatial distribution dominate the stability of rock mass. Because the deformation of rock mass occurs discontinuities in many cases. However in the case of poor quality rock mass under high stresses, the deformation along intact rock can also influence the structure's stability. In this study, two dimensional finite element program was developed with a rheological model to analyze the stability of the structure excavated in jointed rock mass. The “equivalent material” approach was used assuming intact rock, joints and rock bolts as visco-plastic materials. The program was verified by analysing an intact rock model, a jointed rock mass model and a reinforced jointed rock mass model. The displacement was examined in each model with changing the intact rock behaviour as elastic and visco-plastic. In the case of poor quality rock mass under high stresses, e assumption of visco-plastic behaviour of intact rock resulted in larger displacement than when assuming elastic behaviour for intact rock. Therefore it is recommended to add intact rock's visco-plastic behaviour to the existing model, which only assumes visco-plastic behaviour of joints and rock bolts.

• Journal of the Korean Geotechnical Society
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• v.29 no.7
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• pp.75-89
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• 2013

This paper describes a GIS-based geohydrologic methodology, called YSGWF (YonSei GroundWater Flow) for predicting the rainfall infiltration-groundwater flow of slopes. This physical-based model was developed by the combination of modified Green-Ampt model that considers the unsaturated soil parameters and GIS-based raster model using Darcy's law that reflects the groundwater flow. In the model, raster data are used to simulate the three dimensional inclination of bedrock surface as actual topographic data, and the groundwater flow is governed by the slope. Also, soil profile is ideally subdivided into three zones, i.e., the wetting band zone, partially saturated zone, and fully saturated zone. In the wetting band and partially saturated zones the vertical infiltration of water (rainfall) from surface into ground is modeled. When the infiltrated water recharges into the fully saturated zone, the horizontal flow of groundwater is introduced. A comparison between the numerical calculation and real landslide data shows a reasonable agreement, which indicate that the model can be used to simulate real rainfall infiltration-groundwater flow.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.126-132
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• 2016

This study numerically investigates the characteristics of chemical reactions and thermal deformation in a steam reformer. These phenomena are significantly affected by the high-temperature burner gas and the process gas conditions. Because the high temperature of the burner gas ranges from 800 to 1000 K, the reformer tubes undergo substantial thermal deformation, eventually resulting in structural failure. Thus, it is necessary to understand the characteristics of the reaction and thermal deformation under the operating conditions to evaluate the reformer tubes for sustainable, stable operation. Extensive numerical simulations were carried out using commercial CFD code (ANSYS FLUENT/MECHANICA Ver. 13.0) while considering three-dimensional turbulent flows and combined heat transfer including conduction, convection, and radiation. Structural analysis considering conjugated heat transfer between solid tubes and fluid flows was conducted using the Fluid-Solid Interaction (FSI) method. The results show that when the injection temperature of the process gas and burner gas decreased, the hydrogen production rate decreased significantly, and thermal deformation decreased by at least 15 to 20%.

• The Journal of Engineering Geology
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• v.27 no.4
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• pp.429-438
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• 2017

Monte Carlo N-Particle (MCNP) modeling algorithm based on the Monte Carlo method was used to perform the simulation of neutron logging in order to increase the reliability and utilization of neutron logs applied in geological and resource engineering fields. To perform the simulation using MCNP, we used a realistic three-dimensional configuration of neutron sonde and formation. Validation of the modeling was confirmed by comparing the calibration curves of sonde manufacture with those calculated by MCNP modeling. After the validation, lithology effects, pore fluid effects, borehole diameter change, casing effect, and effects of borehole water level were investigated through modeling experiments. Numerical tests indicate that changes in neutron count ratio according to the lithology were quantitatively understood. In case of a borehole with a diameter of 3 inches, ratio of counting rates was higher than expected to be interpreted as borehole fluid has small effects on neutron logging. Effect of casing was also small in general, particular when porosity increases. Since modeling results above the groundwater level showed a tendency opposite to those below the groundwater level, neutron logs can be used to detect groundwater level. The modeling results simulated in this study for various borehole environments are expected to be used for data processing and interpretation of neutron log.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.31-38
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• 2009

The selection of the support system is an important design parameter in design and construction of the tunnel using the new Australian tunnel method. It is a common practice to select the support based on the rock mass grade, in which the rock mass is classified into five rock groups. The method is applicable if the characteristics of the rock mass are uniform in the direction of tunnel excavation. However, such case is seldom encountered in practice and not applicable when the properties vary along the longitudinal direction. This study performs comprehensive three dimensional finite difference analyses to investigate the ground deformation pattern for cases in which the rock mass properties change in the direction of the tunnel axis. The numerically calculated displacements at the tunnel crown show that the displacement is highly dependent on the stiffness contrast of the rock masses. The results strongly indicate the need to select the support type $0.5{\sim}1.0D$ before the rock mass boundary. The paper proposes a new guideline for selecting the support type based the results of the analyses.