• Journal of Biomedical Engineering Research
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• v.43 no.1
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• pp.35-44
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• 2022

Immersed boundary-Lattice Boltzmann Method (IB-LBM) is used for the analysis of flow over the circular cylinder in the concept of fluid-structure interaction analysis (FSI). Recently, IB-LBM has shown the enormous possibility for the application of various biomedical engineering fields, such as the movement of a human body or the behavior of the blood cells and/or particle-based drug delivery system in blood vessels. In order for the numerical analysis of the interaction between fluid and solid object, immersed boundary method and lattice Boltzmann method are coupled to analyze the flow over a cylinder for low Reynolds laminar flow (Re=10, 20, 40 and 100) with Zhu-He boundary condition at the boundary. With the developed IB-LBM, the flow around the cylinder in the uniform flow is analyzed for the laminar flow and the drag and lift coefficients and recirculation length are compared to the previous results.

• Journal of Korean Society on Water Environment
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• v.32 no.3
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• pp.243-252
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• 2016

In cases of water pollution accidents, accurate prediction for arrival time and concentration of contaminants in a river is essential to take proper measures and minimize their impact on downstream water intake facilities. It is critical to fully understand the behavior characteristics of contaminants on river surface, especially in case of oil spill accidents. Therefore, in this study, the effects of main parameters of advection and diffusion of contaminants were analyzed and validated by comparing the results of Lagrangian particle tracking (LPT) simulation of Environmental Fluid Dynamic Code (EFDC) model with those of Global Position System (GPS)-equipped drifter experiment. Prevention scenario modeling was accomplished by taking cases of movable weir operation into account. The simulated water level and flow velocity fluctuations agreed well with observations. There was no significant difference in the speed of surface particle movement between 5 and 10 layer modeling. Therefore, 5 layer modeling could be chosen to reduce computational time. It was found that full three dimensional modeling simulated wind effects on surface particle movements more sensitively than depth-averaged two dimensional modeling. The diffusion range of particles was linearly proportional to horizontal diffusivity by sensitivity analysis. Horizontal diffusivity estimated from the results of GPS-equipped drifter experiment was 0.096 m²/sec, which was considered to be valid for applying the LPT module in this area. Finally, the scenario analysis results showed that particle movements could be stagnant when discharge from the upstream weir was reduced, implying the possibility of securing time for mitigation actions such as oil boom installation and wiping oil contaminants. The outcomes of this study can help improve the prediction accuracy of particle tracking simulation to establish the most suitable mitigation plan considering the combination of movable weir operation.

• Journal of The Geomorphological Association of Korea
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• v.17 no.3
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• pp.31-47
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• 2010

The history of mass movement has been reconstructed from the Angol basin in Guryongcheon drainage basin. Sedimentary facies study, radiocarbon dating, particle size analysis, magnetic susceptibility and geomorphological analysis have been performed to reconstruct the paleo-environmental history of Angol basin. From 40,480 to 9,850yrBP there were five periods of slope instability and from 9,850yrBP to present there were at least four periods of slope instability. Magnetic susceptibility curves match well with the sedimentary facies data. This study may help reconstruct the denudational history of the small basins in Cheonan area and could be the cornerstone of the paleo-climatological study of the Korean Peninsula.

• International Journal of Highway Engineering
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• v.18 no.5
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• pp.39-47
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• 2016

PURPOSES : Road subsidence occurs owing to road cavities, which cause many social and environmental problems, especially in cities. Recently, road cavities were detected by various ground radars and repair works were carried out against the detected cavities. The condition assessments related to the road cavities are necessary to understand the potential risk of the cavities. Therefore, in this study, a numerical study was performed to assess the various conditions of road cavities. METHODS : The numerical method adopted in this study is the discrete element approach, and it is suitable for analyzing the condition because it can consider the movement of the soil particles in the surrounded cavity areas. In addition, the triaxial test was modeled and performed under various cavity conditions inside the specimens. RESULTS : The conditions of different cavity locations and shapes were analyzed to identify the effect of cavity state. Three general cases of particle size distributions were formulated to identify the effect of surrounding ground conditions. As a result, the degree of decrement and volumetric strain were varied depending on the locations and shapes of the cavity. Only minor changes were observed when the particle size distributions were altered. CONCLUSIONS : The strength reduction was higher when the cavity formed was larger and located in the upper zone. Similar to the cavity shape, strength reduction and volume deformation are more influenced by the width than the length of the cavities. There is an influence from ground conditions such as the particle size distribution, especially on the wide cavity.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.108-117
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• 2011

Old train carriages have been used to create artificial reefs (AR) as part of programs to enhance ocean fisheries and recreational resources. This study conducted hydraulic modeling experiments to estimate the structural stability of a train carriage AR. By applying fixed- and movable-bed conditions and Froude similitude, theoretical and hydraulic experiments revealed major design forces(e.g., water waves and currents). The results of this study showed that some dimensionless design parameters (e.g., surf similarity parameters, water particle velocity, scouring, and deposition) also affect the stability of an AR under various wave and current field conditions. In the fixed-bed condition, movement of the AR occurred when dimensionless water particle velocity based on the surf similarity parameter was larger than about 0.32. In the moveable-bed condition, the settlement depth (field values) of the AR ranged from 6 to 30 cm. The results indicated that characteristics of the sediment/bed condition and the direction of external forces acting on an AR should be considered when selecting AR sites.

• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.2
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• pp.15-19
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• 2012

Wood wastes could be renewable resources by recycling as particleboard manufacturing or energy production. Particle board is the most common item of wood waste recycling and energy production from wood wastes has highlighted for energy recovery to reduce greenhouse gas generation in recent years. The aim of this study was to evaluate the environmental benefits of the processes for particle board manufacturing and energy production. The functional unit was one ton of wood wastes and the environmental impact was analyzed by life cycle assessment methodology. The result was that 112kg of carbon dioxide equivalent was produced from particle board manufacturing process and 382kg of carbon dioxide equivalent was produced from combined heat and power generation process. The concept of temporary biomass carbon storage was to applied to this study.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.87-92
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• 2009

An experimental investigation is conducted to study a 2-phase vertically upward hydraulic transport of solid particles by water and non-Newtonian fluids in a slim hole concentric annulus with rotation of the inner cylinder. Rheology of particulate suspensions in viscoelastic fluids is of importance in many applications such as particle removal from surfaces, transport of proppants in fractured reservoir and cleaning of drilling holes, etc. In this study, a clear acrylic pipe was used in order to observe the movement of solid particles. Annular velocities varied from 0.3 m/s to 2.0 m/s. The mud systems included fresh water and CMC solutions. Main parameters considered in the study were inner-pipe rotation speed, fluid flow regime and particle injection rate. A particle rising velocity and pressure drop in annulus have been measured for fully developed flows of water and of aqueous solutions. For both water and 0.2% CMC solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become.

• Journal of the Korean GEO-environmental Society
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• v.15 no.4
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• pp.13-27
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• 2014

Catchments soil erosion, one of the most serious problems in the mountainous environment of the world, consists of a complex phenomenon involving the detachment of individual soil particles from the soil mass and their transport, storage and overland flow of rainfall, and infiltration. Sediment size distribution during erosion processes appear to depend on many factors such as rainfall characteristics, vegetation cover, hydraulic flow, soil properties and slope. This study involved laboratory flume experiments carried out under simulated rainfall in a 3.0 m long ${\times}$ 0.8 m wide ${\times}$ 0.7 m deep flume, set at $17^{\circ}$ slope. Five experimental cases, consisting of twelve experiments using three different sediments with two different rainfall conditions, are reported. The experiments consisted of detailed observations of particle size distribution of the out-flow sediment. Sediment water mixture out-flow hydrograph and sediment mass out-flow rate over time, moisture profiles at different points within the soil domain, and seepage outflow were also reported. Moisture profiles, seepage outflow, and movement of overland flow were clearly found to be controlled by water retention function and hydraulic function of the soil. The difference of grain size distribution of original soil bed and the out-flow sediment was found to be insignificant in the cases of uniform sediment used experiments. However, in the cases of non-uniform sediment used experiments the outflow sediment was found to be coarser than the original soil domain. The results indicated that the sediment transport mechanism is the combination of particle segregation, suspension/saltation and rolling along the travel distance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.6
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• pp.1186-1190
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• 2009

In this paper, we studied on a characteristic of movement of charged particle in equal electric field. In order to fabricate a panel, we used positive charged toner particles of black and negative one of yellow. Panel was biased rectangle pulse without any overshoot. Also, panel's optical characteristics with contrast ratio and viewing angle is measured with RT-200. Response time was measure by using incident laser and detective photodiode. The distribution of m/q of particles by driving in panel throughout the contrast ratio and response time. As a results, driving voltage, contrast ratio, and response time are decided by m/q of charged particles and when m/q of charged particles in panel have regular distribution, it is induce improvement driving characteristics.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.6
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• pp.774-779
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• 2012

Brain-computer interface based on motor imagery is a system that transforms a subject's intention into a control signal by classifying EEG signals obtained from the imagination of movement of a subject's limbs. For the new paradigm, we do not know which positions are activated or not. A simple approach is to use as many channels as possible. The problem is that using many channels causes other problems. When applying a common spatial pattern (CSP), which is an EEG extraction method, many channels cause an overfit problem, in addition there is difficulty using this technique for medical analysis. To overcome these problems, we suggest a binary particle swarm optimization with channel impact factor in order to select channels close to the most important channels as channel selection method. This paper examines whether or not channel impact factor can improve accuracy by Support Vector Machine(SVM).