• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.119-130
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• 2019

This paper establishes an iterative calculation model for the hydrodynamic performance of propeller in oblique flow based on low order potential based surface panel method. The hydrodynamic performance of propeller is calculated through panel method which is also used to calculate the induced velocity. The slipstream of propeller is adjusted according to the inflow velocity and the induced velocity. The oblique flow is defined by the axial inflow velocity and the incident angle. The calculation results of an instance show that the thrust and torque of propeller decrease with the increase of axial inflow velocity but increase with the incident angle. The unsteadiness of loads on the propeller blade surface gets more intensified with the increases of axial inflow velocity and incident angle. However, comparing with the effect of axial inflow velocity on the unsteadiness of the hydrodynamic performance of propeller, the effect of the incident angle is more remarkable.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.748-755
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• 2007

To develop an efficient pump operating rule for a retard basin, it is necessary to estimate inflow to the retard basin accurately which is affected by the backwater effect at the outlet of the conduit. The magnitude of the backwater effect is dependent on the water depth of a retard basin; however, the depth is determined by the amount of inflow and outflow. Thus, a real time simulation system that is able to simulate urban runoff and the pump operation with the consideration of the backwater effect is required to estimate the actual inflow to a retard basin. With this system, the efficient pump operating rule can be developed to diminish the possible flood damage on urban areas. In this study, a realtime simulation system is developed using the SWMM 5.0 DLL and Visual Basic 6.0 equipped with EXCEL to estimate inflow considering the backwater effect. The realtime simulation can be done by updating realtime input data such as minutely observed rainfall and the depth of a retard basin. Using those updated input data, the model estimates actual inflow, the amount of outflow discharged by pumps and gates, the depth of each junction, and flow rate at a sewer pipe on realtime basis. The developed model was applied to the Joonggok retard basin and demonstrated that it can be used to design a sewer system and to estimate actual inflow through the inlet sewer to reduce the inundation risk. As results, we find that the model can contribute to establish better operating practices for the pumps and the flood drainage system.

• Korean Journal of Materials Research
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• v.26 no.11
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• pp.662-669
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• 2016

In order to identify changes in the nature of the particles due to changes in the inflow rate of the raw material solution, the present study was intended to prepare nano-sized cobalt oxide ($Co_3O_4$) powder with an average particle size of 50 nm or less by spray pyrolysis reaction using raw cobalt chloride solution. As the inflow rate of the raw material solution increased, droplets formed by the pyrolysis reaction showed more divided form and the particle size distribution was more uneven. As the inflow rate of the solution increased from 2 to 10 ml/min, the average particle size of the formed particles increased from about 25 nm to 40 nm, while the average particle size did not show significant changes when the inflow rate increased from 10 to 50 ml/min. XRD analysis showed that the intensity of the XRD peaks increased remarkably when the inflow rate of the solution increased from 2 to 10 ml/min. On the other hand, the peak intensity stayed almost constant when the inflow rate increased from 10 to 50 ml/min. With the increase in the inflow rate from 2 to 10 ml/min, the specific surface area of the particles decreased by approximately 20 %. On the contrary, the specific surface area stayed constant when the inflow rate increased from 10 to 50 ml/min.

• Journal of the Korean Operations Research and Management Science Society
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• v.38 no.3
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• pp.71-86
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• 2013

This research explores the question how interactions between customer and firm affect firm growth. To test suggested hypotheses, this study collects data on social commerce industry in Korea during the period from the beginning of social commerce industry in Korea, May 2010, to March 2012, and investigates the effect of social media on the growth of social commerce firms. We suggest two hypotheses in this study. First, as web traffic inflow through social media into a focal social commerce increases, the growth rate of the focal social commerce increases. Second, the more diverse social media channel through which web traffic inflows into a focal social commerce, the weaker the positive effect of web traffic inflow on the growth rate of the focal social commerce. Analysis of data shows that inflow through social media is positively related to the growth of social commerce. In addition, our analysis shows that inflow channel diversity weakens the positive relationship between web traffic inflow through social media and growth rate of social commerce firms. These results suggest that firms need to concentrate on few social media in order to attract customers. The study contributes to understanding how interaction between firms and customers influences the growth of the firm.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.3
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• pp.68-74
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• 2004

Effect of fluctuation imposed on the inflow to LOX manifold of liquid rocket has been analyzed numerically. Time-varying fluctuation was idealized by the sinusoidal signal and three different representative frequencies were considered. It was found that all the frequencies tested produced the consistent flow reactions in the manifold in that the place close to the region of infection showed oscillatory flow rate through injector orifices in phase with the inflow fluctuation whereas the other side exhibits characteristics which are out of phase.

• East Asian Economic Review
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• v.17 no.2
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• pp.129-159
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• 2013

Over the course of the recent global financial crisis, emerging economies experienced massive swings in capital inflows. In this paper, we estimate a VAR model to assess the impact of capital inflow shocks, which are identified using a set of sign restrictions, on house prices in Korea. We base the analysis on three alternative measures of capital inflows: net total inflows, net portfolio inflows and gross total inflows. The results suggest that capital inflow shocks have a significantly positive and persistent effect on real house prices. Although shocks to capital inflows are found to be substantially more important for Korean asset markets than for other OECD countries, their overall explanatory power is modest. Using regional house price data we also show that capital inflow shocks have an asymmetric effect on property markets across the seven largest Korean cities and across different parts of Seoul.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.23-33
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• 2009

The inherent aeromechanical complexity of a rotor system necessitated the comprehensive analysis code for helicopter rotor system. In the present study, an aerodynamic analysis module has been developed as a part of rotorcraft comprehensive program. Aerodynamic analysis module is largely classified into airload calculation routine and inflow analysis routine. For airload calculation, quasi-steady analysis model is employed based on the blade element method with the correction of unsteady aerodynamic effects. In order to take unsteady effects - body motion effects and dynamic stall - into account, aerodynamic coefficients are corrected by considering Leishman-Beddoes's unsteady model. Various inflow models and vortex wake models are implemented in the aerodynamic module to consider wake induced inflow. Specifically, linear inflow, dynamic inflow, prescribed wake and free wake model are integrated into the present module. The aerodynamic characteristics of each method are compared and validated against available experimental data such as Elliot's induced inflow distribution and sectional normal force coefficients of AH-1G. In order to validate unsteady aerodynamic model, 2-D unsteady model for NACA0012 airfoil is validated against aerodynamic coefficients of McAlister's experimental data.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.4
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• pp.30-37
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• 2004

Flow characteristics of the inflow ahead of a rotating propeller attached to a container ship model were investigated using a two-frame PIV (Particle Image Velocimetry) technique. Ensemble-averaged mean velocity fields were measured at four different blade phases. The mean velocity fields show the acceleration of inflow due to the rotating propeller and the velocity deficit in the near-wake region. The axial velocity distribution of inflow in the upper plane of propeller is quite different from that in the lower plane due to the thick hull boundary layer. The propeller inflow also shows asymmetric axial velocity distribution in the port and starboard side. As the inflow moves toward the propeller, the effect of phase angle variation of propeller blade on the inflow becomes dominant. In the upper plane above the propeller axis the inflow has very low axial velocity and large turbulent kinetic energy, compared with the lower plane. The boundary layer developed along the bottom surface of stern hull forms a strong shear layer affecting vortex structure of the propeller near-wake.

• The Journal of the Convergence on Culture Technology
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• v.10 no.3
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• pp.111-119
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• 2024

The purpose of study is to analyze the effect of population inflow on apartment price growth. For this purpose, proxy for population structure is employed: (i) net population inflow based on 'resident registration criteria', (ii) buyer's transaction. The major findings are as followed. First, net population inflow of total and 50 over gives no significant effects on the apartment price growth in Seoul and Jeju. However, there are significant and positive effects of 50s and 60s in Seoul, and 60s in Jeju on the apartment price growth, respectively. Second, buyer's transactions of 'total and 50 over' give positive effect on apartment price growth only in Seoul. However, 60s and 50s of buyers' transaction give positive effect on the apartment price growth both in Seoul and Jeju. This study implies that more detailed population inflow like age group provide more meaningful information to the study on apartment price growth.

• Wind and Structures
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• v.30 no.6
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• pp.597-616
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• 2020

The blockage effect on the aerodynamic characteristics of tall buildings is a fundamental issue in wind tunnel test but has rarely been addressed. To evaluate the blockage effects on the aerodynamic forces on a square tall building and flow field peripherally, large eddy simulations (LES) were performed on a 3D square cylinder with an aspect ratio of 6:1 under the uniform smooth inflow and turbulent atmospheric boundary layer (ABL) inflow generated by the narrowband synthesis random flow generator (NSRFG). First, a basic case at a blockage ratio (BR) of 0.8% was conducted to validate the adopted numerical methodology. Subsequently, simulations were systematically performed at 6 different BRs. The simulation results were compared in detail to illustrate the differences induced by the blockage, and the mechanism of the blockage effects under turbulent inflow was emphatically analysed. The results reveal that the pressure coefficients, the aerodynamic forces, and the Strouhal number increase monotonically with BRs. Additionally, the increase of BR leads to more coherence of the turbulent structures and the higher intensity of the vortices in the vicinity of the building. Moreover, the blockage effects on the aerodynamic forces and flow field are more significant under smooth inflow than those under turbulent inflow.