• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.1
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• pp.100-109
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• 2012

Removal rates of $PO_4-P$ and TP in a free water surface wetland system were investigated. The system was established in 2008 on a floodplain in the middle reach of the Gwangju Stream flowing through Gwangju City. Its dimensions were 46 meters in length and 5 meters in width. Two year old Typha angustifloria L. growing in pots were planted on half of the area and Zizania latifolia Turcz on the other half in 2008. Stream water was funneled into the wetlands by gravity flow, and its effluent was discharged back into the stream. The influent volume was controlled by valves and water depth was adjusted by wires. Volume and water quality of inflow and outflow were analyzed from January to December in 2010. Inflow into the system averaged approximately $710m^3/day$ and hydraulic residence time was about 1.5 hours. Average influent and effluent $PO_4-P$ concentration were 0.144 and 0.103mg/L, respectively, and $PO_4-P$ abatement amounted to 28.6%. Influent and effluent TP concentration averaged 0.333 and 0.262mg/L, respectively, and TP retention reached to 20.7%.$PO_4-P$ removal rate(%) during plant growing season(31.448) was significantly high(p<0.001) when compared with that during plant non-growing season(25.829). TP abatement rate(%) during plant growing season(27.230) was also significantly high(p<0.001) when compared with that of the non-growing season(14.856). Major phosphorous removals in the system resulted from adsorption of phosphorous in the litter-soil layers; sedimentation of particulate phosphorous and Ca, Al, Fe bounded phosphates; and absorption of phosphorous by emergent plants. The adsorption and sedimentation occurred throughout the year, however, the absorption took place during plant growing season. This resulted in higher removals of $PO_4-P$ and TP during plant growing season.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.2
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• pp.161-168
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• 2015

In this paper, we present an inertial sensor-based gait distance measurement system using accelerometer, gyroscope, and magnetometer. To minimize offset and gain error of inertial sensors, we performed the calibration using the self-made calibration jig with 9 degrees of freedom. For measuring accurate gait distance, we used gradient descent algorithm to remove gravity error and used analysis of gait pattern to remove drift error. Finally, we measured a gait distance by double-integration of the error-removed acceleration data. To evaluate the performance of our system, we walked 10m in a straight line indoors to observe the improvement of removing error which compared un-calibrated to calibrated data. Also, the gait distance measured by the system was compared to the measurement of the Vicon motion capture system. The evaluation resulted in the improvement of $31.4{\pm}14.38%$(mean${\pm}$S.D.), $78.64{\pm}10.84%$ and $69.71{\pm}26.25%$ for x, y and z axis, respectively when walked in a straight line, and a root mean square error of 0.10m, 0.16m, and 0.12m for x, y and z axis, respectively when compared to the Vicon motion capture system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.2
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• pp.151-160
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• 2002

A modeling system for three-dimensional flow (FEMOS) has been developed and applied to simulate the tidal currents of Asan Bay. The system can consider tidal flats changing with time and uses a finite element method that can adapt coastline change effectively. The simulation results for Asan Bay with large tidal flats, shallow water depth and high tidal range showed good agreements with the observed currents of long-term variations at the medium layer and short-term variations of vertical profiles. Based on the simulated tidal currents, the horizontal distributions of bottom shear stress were calculated and showed close relation with the change of bottom topography. The system can be used widely to study coastal circulation in the coastal region with complex geography.

• The Transactions of the Korea Information Processing Society
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• v.7 no.2
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• pp.355-364
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• 2000

Application sharing for collaborative works make multiple participants to be capable of collaborative developments through sharing development tools and applications which is distributed to various system without spatial restriction. However, applying legacy application sharing to CSCW based virtual environment has a problem because it dont consider 3D space and it disturbs the harmonic interaction of participants. In this study, we designed application sharing system for collaborative works in 3D virtual environment to share application effectively on collaborative virtual environment. The designed application sharing system for collaborative works in 3D virtual environment consist of application sharing manager, group manager and communication manager. This system is able to perceive event of 3D space about application of participant on 3D virtual environment by agent which moves to participant sites and get an ordered events and conflict among participants through scheduling. Therefore, designed application sharing system for collaborative work in 3D virtual environment can support efficient collaborative works and improve reusability of legacy application through using easily legacy application in 3D virtual environment when CSCW application development for virtual environments.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.2
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• pp.21-30
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• 1990

Theoretical and experimental techniques to analyze the two-dimensional liquid motion in a tank are discussed. A Lagrangian FEM with a velocity correction procedure is introduced to describe incompressible free surface fluid flow. A mesh rezoning technique is used to prevent strong distortion of finite elements in the Lagrangian description. Model test technique for sloshing tank is developed using a hydraulic type bench tester. The influence of the variation in the exciting frequency and amplitude are observed for various fill depths. The results of theoretical calculations are compared with those of experiments.

• Smart Media Journal
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• v.8 no.2
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• pp.80-85
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• 2019

Generally, interlayer noise is measured in decibels (A) in terms of free field. In this paper, we propose a measurement method of interlayer vibration acceleration in the diffusion field perspective. The proposed method can represent a vibration-embodied formula similar to the sensitivity of earthquake intensity when the natural vibration of apartment house is measured by acceleration with its average value of $20mm/s^2$ represented by an the geometric progression of radix. Based on this theory, this paper proposes a method to show the optimal user experience (UX) by applying the interlayer vibration acceleration of the epicenter to the system of human - computer interaction (HCI).

• Journal of Korea Port Economic Association
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• v.24 no.2
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• pp.175-192
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• 2008

Today's individual firms no longer compete as solely autonomous entities, but rather as supply chain. As such the competitive position of a port is not only determined by its internal strengths but also it is also affected by its links in a global supply chin. In other words, port competitiveness is becoming increasingly dependent on external coordination and control of the whole supply chain. The main purpose of this paper is to examine how a port embeds itself into supply chain in order to strengthen its competitive position by focusing on Dubai port case. This paper found that Dubai port used three phases-insertion, integration and dominance-as a strategies for how it can embedded into global supply chain successfully. Dubai's global supply chain strategies give some implications for the further development of the Port of Gwangyang. First, the Port of Gwangyang should fully utilize symbiotic relationship with Gwangyang free Economic Zone. Second, the integration between Korea Container Terminal Authority and GYFEZ can be recommended for fast decision-making and providing a one-stop-service. Finally, Gwangyang should pursue an aggressive supply chain strategy, aims at dominance in the regional port network through port alliance with small and medium ports in neighboring area.

• Journal of Korea Port Economic Association
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• v.26 no.1
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• pp.195-221
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• 2010

Kunsan port based on the selection of Kunsan Free Trade Area is expected to develop into a regional beach-head port and foreign investment area, and as the result it will play a great role in accelerating the coming age of the west sea. To promote the foreign competitiveness of Kunsan port as a central container port it can be pointed out that 1) to raise up the utilization ratio of Kunsan port as the front base of export and import by multinational corporations, 2) to hustle up the development of Kunsan container port toplay the central role as the composite container linkage central port, 3) to strengthen the attraction activities of foreign investment into the Kunsan Free Trade Area for the balanced development between regions in nation, 4) the support of both central and local governments to accelerate the comingage of the west sea are necessary.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.9-18
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• 2016

The slender structures such as high rise building or marine riser are highly susceptible to dynamic force exerted by fluid-structure interactions among which vortex-induced vibration(VIV) is the main cause of dynamic unstability of the structural system. If VIV occurs in natural frequency regime of the structure, fatigue failure likely happens by so-called lock-in phenomenon. This study presents the numerical analysis of dynamic behavior of both structure and fluid in the lock-in regimes and investigates the subjacent phenomena to hold the resonance frequency in spite of the change of flow condition. Unsteady and laminar flow was considered for a two-dimensional circular cylinder which was assumed to move freely in 1 degree of freedom in the direction orthogonal to the uniform inflow. Fluid-structure interaction was implemented by solving both unsteady flow and dynamic motion of the structure sequentially in each time step where the fluid domain was remeshed considering the movement of the body. The results show reasonable agreements with previous studies and reveal characteristic features of the lock-in phenomena. Not only the lift force but also drag force are drastically increasing during the lock-in regime, the vertical displacement of the cylinder reaches up to 20% of the diameter of the cylinder. The correlation analysis between lift and vertical displacement clearly show the dramatic change of the phase difference from in-phase to out-of-phase when the cylinder experiences lock-in. From the results, it can be postulated that the change of phase difference and flow condition is responsible for the resonating behavior of the structure during lock-in.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.594-602
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• 2010

Since the requirement of the high density integration and thin package technique of semiconductor have been increasing, the main package type of semiconductor will be a chip scale package (CSP). The changes of diffusion coefficient and moisture content ratio of epoxy resin systems according to the change of liquid type epoxy resin and fillers for CSP applications were investigated. The epoxy resins used in this study are RE-304S, RE310S, and HP-4032D, and Kayahard MCD as hardener and 2-methylimidazole as catalyst were used in these epoxy resin systems. The micro-sized and nano-sized spherical type fused silica as filler were used in order to study the moisture absorption properties of these epoxy molding compound (EMC) according to the change of filler size. The temperature of glass transition (Tg) of these EMC was measured using Dynamic Scanning Calorimeter (DSC), and the moisture absorption properties of these EMC according to the change of time were observed at $85^{\circ}C$ and 85% relative humidity condition using a thermo-hygrostat. The diffusion coefficients in these EMC were calculated in terms of modified Crank equation based on Ficks' law. An increase of diffusion coefficient and maximum moisture absorption ratio with Tg in these systems without filler can be observed, which are attributed to the increase of free volume with Tg. In the EMC with filler, the changes of Tg and maximum moisture absorption ratio with the filler content can be hardly observed, however, the diffusion coefficients of these systems with filler content show the outstanding changes according to the filler size. The diffusion via free volume is dominant in the EMC with micro-sized filler; however, the diffusion with the interaction of absorption according the increase of the filler surface area is dominant in the EMC with nano-sized filler.