• Journal of Ship and Ocean Technology
• /
• v.4 no.2
• /
• pp.13-23
• /
• 2000

A low-order potential based boundary element method is applied to the prediction of the flow around the cavitating propeller in steady or in unsteady inflow. For given cavitation number, the cavity shape is determined in an iterative manner until the kinematic and the dynamic boundary conditions are both satisfied on the approximate cavity boundary. In order to improve the solution behavior near the tip region, a hyperboloidal panel geometry and a modified split panel method are applied. The method is then extended to include the analysis of time-varying cavitating flows around the propeller blades via a time-step algorithm in time domain. In the method, the steady state oscillatory solution is obtained by incremental stepping in the itme domain. Finally, the present method is validated through comparison with other numerical results and experimental data.

• International Commerce and Information Review
• /
• v.9 no.3
• /
• pp.23-32
• /
• 2007

The purpose of this study is to estimate and analyse the relationship between efficiency of bank industry and macroeconomic variables. We employ Johansen's multivariate cointegration methodology, since the model must be stationary to avoid the spurious results. The empirical results show that our model is stationary as well as mean-reverting. This paper also applies impulse-response functions to get additional information regarding the responses of the bank spread to the shocks economic variables such as long and short term interest rates differential, banking organ liquidity, business cycle index, and foreigner's net equity investment. The results indicate that while the bank spread respond positively to liquidity and equity investment shocks and then decay very quickly.

• Water Engineering Research
• /
• v.3 no.3
• /
• pp.155-162
• /
• 2002

This study presents the theoretical approach for volume concentration, velocity profile, and granular discharge on the fluid-granule mixed flow downstream of the scour hole at the outlet of the hydraulic structure. Concept of dilatant model was applied for the stress-strain relationships of fluid-granule mixed flow since the flow downstream of the scour hole corresponds to debris flow, where momentum transfers through particle collisions. Mathematical formulations were derived using momentum equation and stress-strain relation of the fluid-granule mixture. Velocity profile under the assumption of uniform concentration over flowing layer showed the downward convex type. Deposition angle of downstream hump was found to be a function of an upstream slope angle, a dynamic friction angle and a volume concentration irrespective of flow itself, Granular discharge and the overflow depth were obtained with given values of inflow rates. Experimental results showed relatively good agreements with theoretical ones.

• East Asian Economic Review
• /
• v.25 no.2
• /
• pp.151-174
• /
• 2021

This paper empirically examines whether and how inward foreign direct investment (FDI) affected industrial productivity in Korea during the 2000-2016 period, based on dynamic panel data of inflow FDI on an arrival basis from 427 manufacturing industries. The paper adds to the literature by analyzing whether both technology spillovers and industrial restructuring from inward FDI can differ according to industrial characteristics such as capital intensity, imported intermediate inputs, and tariffs. The empirical results show that the overall effects of inward FDI on total factor productivity (TFP) were statistically insignificant in general. However, the positive effects of inward FDI on productivity became statistically significant for industries with lower tariffs. Capital intensity were not involved in the relationship between inward FDI and productivity. Thus, the paper highlights that the results in previous studies with inward FDI on a notification basis were overestimated and inward FDI policies in Korea should focus on channels such as trade liberalization and the redistribution of production factors rather than capital accumulation.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.52 no.2
• /
• pp.68-79
• /
• 2003

We estimated harmonics on power system of AC railway based on quantitatively measured harmonics and investigated the need of facilities for harmonics reduction. In order to analysis harmonics which inflow into power system due to increase in collector voltages and harmonic currents generated from the train when the railway is in operation, the railway system Is sectioned into power supply, railway line, AT, sectioning Post and subsectioning post. For analysis of extension of currents resulting from the railway loads, PWM converter, VVVF inverter and the feeder system are modeled based on the dynamic node technique(DNT). In order to test the usefulness of the DNT for analysis of harmonic effects, the measured harmonic currents and harmonic magnification ratios at the S/K substation are compared with simulation results using DNT modelling, which include the results for two cases with and without filters for suppression of harmonic currents. When 8 cars(4M4T) are in operation, the total sum of harmonic currents resulting from the train at M and T phases, which inflow into the substation along with the railway line, is calculated. Using the harmonics analysis program for railway feeder system with these data, the total harmonic distortion factor(710) at the outgoing point of KEPCO substation is computed. The calculation shows that when the maximum THD at the receiving point of H/K substation was 0.0443% which is much lower than 1.5% which is the allowable value of KEPCO at 154kV as well as IEEE-519 above 132kV This result indicates that any measure for harmonics reduction in Incheon International Airport Railway is not needed.

• Wind and Structures
• /
• v.23 no.4
• /
• pp.313-350
• /
• 2016

Taipei 101 Tower, which has 101 stories with height of 508 m, is located in Taipei where typhoons and earthquakes commonly occur. It is currently the second tallest building in the world. Therefore, the dynamic performance of the super-tall building under strong wind actions requires particular attentions. In this study, Large Eddy Simulation (LES) integrated with a new inflow turbulence generator and a new sub-grid scale (SGS) model was conducted to simulate the wind loads on the super-tall building. Three-dimensional finite element model of Taipei 101 Tower was established and used to evaluate the wind-induced responses of the high-rise structure based on the simulated wind forces. The numerical results were found to be consistent with those measured from a vibration monitoring system installed in the building. Furthermore, the equivalent static wind loads on the building, which were computed by the time-domain and frequency-domain analysis, respectively, were in satisfactory agreement with available wind tunnel testing results. It has been demonstrated through the validation studies that the numerical framework presented in this paper, including the recommended SGS model, the inflow turbulence generation technique and associated numerical treatments, is a useful tool for evaluation of the wind loads and wind-induced responses of tall buildings.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.125-125
• /
• 2023

Estuarine dams are dams constructed in estuaries for reasons such as securing freshwater resources, controlling water levels, and hydroelectric power generation. These estuarine dams alter the flow of freshwater to the coastal ocean and the tidal properties of the estuaries which has implications for the estuaries' circulation and sediment transport. A previous study has analyzed the effect of estuarine dams on 1D (along-channel) circulation and sediment transport. However, the effect of estuarine dams on the transverse variability of along-channel and across-channel circulation and sediment transport has not been studied and is not known. In this study, a coupled hydrodynamic-sediment dynamic numerical model (COAWST) was used to analyze the transverse variability of along-channel and across-channel flow and sediment transport in estuaries with estuarine dams. The estuarine dam was found to change the 3D structure of circulation and sediment transport, and the result was found to depend on the estuarine type (i.e., strongly stratified (SS) or well-mixed (WM) estuary). The SS estuary had inflow in the channel and outflow over the shoals, consistent with estuarine circulation. Longer discharge interval reduced the estuarine circulation. The WM estuary had inflow over the shoals and outflow in the channel, consistent with tide-induced circulation. As the estuarine dam was located nearer to the estuary mouth, the tide-induced circulation was reduced and replaced with estuarine circulation. The lateral circualtion was the greatest in the tide-dominated estuaries. It was reduced and changed direction due to differential advection change as the dam was located nearer the mouth. Overall, the WM estuary transverse flow structure changed the most. Lateral sediment flux was important in all estuaries, particularly for transporting sediments to the tidal flats.

• Knowledge Management Research
• /
• v.22 no.3
• /
• pp.17-29
• /
• 2021

The purpose of this study is to analyze investment performance by applying dynamic methodologies that reflect market expectations rather than traditional static methodologies in applying the glide path of target date fund. In calculating market expectations, the number of distributed shares in the ETF market was used, and the dynamic glide path model portfolio considering market expectations in the analysis period from late 2011 to October 2020 could show better results than the existing static glide path. According to the analysis, increasing the portion of risky assets at a time when the number of shares in the ETF's distribution increases, and in the opposite case, reducing the portion of risky assets is advantageous for profit. The results of this study are expected to provide useful theoretical and practical implications for researchers and asset management workers who are interested in knowledge management from a broad perspective beyond the boundary of pension asset management to the public fund market and ETF market.

• Journal of Biomedical Engineering Research
• /
• v.25 no.4
• /
• pp.295-300
• /
• 2004

Coil embolization technique has been used recently to treat cerebral aneurysms. When a giant or a multilobular aneurysm are treated by roils, filling an aneurysm sac completely with coils is difficult and partial blocking of an aneurysm sac is inevitable. Blood flow characteristics, which nay affect the embolization process of an aneurysm sac, are changed by the locations of coils for the Partially blocked aneurysms. Blood flow fields are also influenced by the geometry of a parent vessel. In order to suggest the coil locations effective for aneurysm embolization, the blood flow fields of lateral aneurysm models were analyzed for the different coil locations and parent vessel geometries. Three dimensional pulsatile flow fields are analyzed by numerical methods considering non-Newtonian viscosity characteristics of blood. Flow rate into the aneurysm sac (inflow rate) and wall shear stress, which are suspected as flow dynamic factors influencing aneurysm embolization, are also calculated. Inflow rates were smaller and the low wall shear stress zones were larger in the neck blocked models compared to the dome blocked models. Smaller inflow and larger low wall shear stress zones in the distal neck blocked model imply that the distal neck should be the effective coil locations for aneurysm embolization.

• Journal of Korean Society of Environmental Engineers
• /
• v.39 no.12
• /
• pp.706-713
• /
• 2017

This study compared and analyzed the water treatment efficiency and the applicability of water treatment plant using the existing Mechanical Rapid-Mixer by introducing the Non-powered Vortex Mixer to the domestic water treatment plant. For this study, fluid flow characteristics and head loss of a Non-powered Vortex Mixer are calculated by Computational Fluid Dynamics (CFD)respectively. The head loss rate inside the mixer was 11.30% when the inflow velocity was 0.5 m/sec, 16.27% at 0.6 m/sec and 21.44% at 0.7 m/sec, the head loss rapidly increased at the optimal velocity of 0.5 m/sec. For the inflow velocity of 0.5 m/sec, the turbulent intensity at the inlet was 2.37% and at the outlet was 7.83%, so there was sufficient mixing strength for the particulate matter and the coagulant. The result of the water quality of the treatment plants with the inflow velocity of 0.38 m/sec that was operated in three years after replacing all 12 units of the existing Rapid-Mixer with the Non-powered Mixer met the standards. Hence, it is possible to reduce the energy consumption of 64,143 ~ 65,306 kWh/year since the Rapid-Mixer is replaced by the Non-powered Vortex Mixer.