• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.11
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• pp.3003-3013
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• 1995

The characteristics of the flow field in the tangentially fired furnace are presented. Experiments are conducted in the simplified cold type isothermal flow model. In the measurement of flow field, a hot wire anemometer is used. The hot wire was calibrated by lookup table method. The mean velocity field and turbulence characteristics are showed with changing the nozzle angle. In the center of the model, the low speed, unstable flow region is formed. The size and position of these regions are varied with changing the nozzle angle. It can be used as fundamental data in the design of the large furnace. From the experimental results, various turbulent characteristics of swirling flow field is obtained. And the entrainment mechanism of the jet flow field is described from the distribution of the skewness and the flatness. It can be used the raw data of approximate calculation and turbulent modelling.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.1-12
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• 1990

The study is concerned with the analysis of combined forging of non-axisymmetric shapes with inclined protrusions by UBET technique. Work hardening is considered for the given range of strain rate during the forging process. A complex shape with inclined cavities is analyzed by subdividing the workpiece into finite UBET elements for which simple velocity fields are applicable. An experimental set-up was designed and manufactured for the experiment, and experiments are carried out with lead billets. The devised set-up can be used for closed-die forging of complex shapes with protrusions in which the dies can be separated automatically for easy removal of the forged products. Based on the derived kinematically admissible velocity fields for corresponding UBET elements, general computer programs have been developed. Since the energy dissipation rate for each elemental region is provided by subprograms (Subroutine or Function), the developed program can be applied to the forging problems of various shapes. The present study has shown that the method developed can be effectively applied to forging of non-axisymmetric shapes with complicated protrusions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.825-834
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• 2008

Nose chine shape optimization study has been performed to maximize the directional stability at high angle of attack supersonic flow. Various chine shapes are generated using super ellipse equation. By numerically investigating the directional stability characteristics of those shapes, the baseline configuration for the shape optimization has been selected using the three-dimensional Navier-Stokes equations. The configuration is represented by the NURBS curves which can adjust the surface geometry by the control points. The response surfaces are constructed to obtain optimum shape which has high directional stability characteristics and lift-to-drag ratio. From this study, an efficient configuration design and optimization process which utilizes the parameter-based configuration generation techniques and approximation method has been established, then 29% improvement of the directional stability by strong vortexes from chine nose is accomplished.

• The Journal of the Korea Contents Association
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• v.15 no.8
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• pp.473-480
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• 2015

The purpose of this study is to analyze the influence of the cash flow of pharmaceutical companies on R&D investment. 143 pharmaceutical companies listed in the KOSDAQ market from 2009 to 2013. Financial statements and comments in general and internal transactions were extracted from TS-2000 of the Korea Listed Company Association (KLCA), and data related to stock price was extracted from KISVALUE-III of NICE Information Service Co., Ltd. STATA 12.0 was used as the statistical package for panel analysis. The summary of the findings and the interpretation of the significance of this are as follows: First, the current ratio (internal finance) had a positive influence on R&D investment. Second, the debt ratio (external finance) had a negative influence on R&D investment. The pharmaceutical company prefers internal funds to external funds due to the asymmetry of information in the loan markets. In other words, this shows why internal finances have a significant influence on R&D investment at pharmaceutical companies.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.20 no.2
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• pp.201-210
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• 1990

The purpose of this study was to observe the relationship between mandibular asymmetry and Temporomandibular Disorders by means of the cephalometry using the posteroanterior cephalogram and the submentovertex cephalogram which were taken in 35 Temporomandibular Disorder patients and 35 normal persons ranged from 20S to 30S. The results were as follows: 1. The angulation which was formed by the median line with the ANS-Menton line (MAP) was greater in patients group and there was statistically significant difference. 2. The angulation which was formed to the median line with the Menton-Odontoid process tip line (MES), the difference of the distances from the center of the posterior surface of the both condyles to the most anterior point of the chin (DD), the difference of the distances from the center of the both condyles to the horizontal reference line (DE), the difference of the angulations which were formed by the both condyles axes with the horizontal reference line (DCE), the difference of the lengths of the both condyles (CL) and the difference of the widths of the both condyles (DW) were greater in patients group and there were statistically significant differences. There was reversed correlation between MAP and the difference of the distances from the 3. bilateral points of the lateral margin of the both zygomaticofrontal sutures to the at the lateral inferior margin of the both antegonial protuberances in mandible (DH). There was reversed correlation between MES and DD, DE, DCE. 5. There was correlation between MAP and MES.

• Journal of Korea Water Resources Association
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• v.41 no.6
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• pp.575-585
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• 2008

It is essential to obtain accurate and highly reliable streamflow data for water resources planning, evaluation and management as well as design of hydraulic structures. A new discharge computation method proposed in this research uses Chiu's velocity distribution and estimation of maximum velocity. This method shows acceptable channel discharges comparing these by the exiting velocity-area method. When velocity-area method is used, it is required to observe velocities at every specified point and vertical line using a velocity meter like Price-AA. If the method proposed in this research, is used, however it is not necessary to observe all point velocities needed in the velocity-area method. But this method can not be applied for the cases of very complex and strongly asymmetric channel cross-sections because Chiu's velocity distribution using entropy concept may be quite biased from that of natural rivers.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.61-71
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• 1997

Numerical and experimental studies are carried out to analyse the resistance characteristics of a hydrofoil catamaran which is advancing on calm water with uniform speed. For the hydrofoil catamaran with modified Wigley hull which has asymmetric transverse section and transom stem, the studies are carried out for the range of Froude number 0.2 to 1.0 and the angle of attack of the hydrofoil $0.0^{\circ}$ to $3.0^{\circ}$. The model tests are carried out in the ship model basin of Inha University. Also the numerical computations using a finite difference method are performed for the simulations of fluid flow around the hull form and the results are compared with the results of the model tests. The present computation results show well quantitative agreement with the experimental results. The experimental results show that the shape and angle of attack of the foils exerts a considerable influence on the running posture and resistance performance of ship.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.3
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• pp.110-115
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• 2023

During the Hg₂Br₂ physical vapor transport process, with increasing the partial pressure of component B, P_B from 40 Torr to 200 Torr, a unicellular convective flow structures move from the crystal growth region to the center region in the vapor phase. The boundary layer flow is dominant for P_B = 40 Torr, and the core region flow is dominant for P_B = 200 Torr. The flow in the vapor phase shows a three-dimensional convective flow structure with a single cell (unicellular) for P_B = 40 Torr and 200 Torr, exhibits an asymmetrical flow with respect to the x, y central axis under the horizontally oriented configuration with an aspect ratio (length-to-width) of 3 and linear conducting walls. The critical temperature difference between the source and crystal region is about 30 K. The total molar flux of Hg₂Br₂ increases with the temperature difference until the total molar flux reaches the critical value. At the critical total molar flux, the total molar flux abruptly decreases.

• Journal of Navigation and Port Research
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• v.43 no.6
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• pp.369-376
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• 2019

Ship hydrodynamics in the confined waterways is challenging. When a ship is maneuvering in confined waterways, the hydrodynamic behavior may vary significantly because of the hydrodynamic interaction between the bottom of the ship hull and the seabed, or so-called shallow water effects. Thus, an accurate prediction of shallow water and bank effects is essential to minimizing the risk of the collision and the grounding of the ships. The hydrodynamic derivatives measured by the virtual captive model test provide a path to predicting the change in ship maneuverability. This paper presents a numerical simulation of captive model tests to predict the maneuverability of a ship in confined waterways. Also, straight and zig-zag simulation were conducted to predict the trajectory of a ship maneuvering in confined waterways. The results showed that the asymmetric flow around a ship induced by vicinity of banks causes pressure differences between the port and starboard sides and the trajectory of a ship maneuvering in confined waterways.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.5
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• pp.589-600
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• 2019

In order to investigate the flow structures around Geumo archipelago on Southern Waters of Korea, water movements were measured for 25 hours during spring tide in May and neap tide in September 2002 using ADCP (Acoustic Doppler Current Profiler) attached to a running boat. Dominant directions of ebb and flood current at spring tide are SE-NW, representing the average flow rate of approximately 40cm/s in the surface layer. However because of the topographical reason, the direction and speed of the flow in the narrow waterway sea area around the northwest of Gae Island were different. There was no notable baroclinic component of tidal flow at spring tide. This indicates that the sea area has been actively engaged in vertical mixing due to island wake or eddy due to narrow waterways, shallow water depth and rapid flow rate around archipelago. At neap tide, dominant directions of tidal flows are SSE-NNW and the average flow rate in the surface layer is about 85 percent of the spring tide. The duration and intensity of the flow direction are shorter and less dominant than the spring tide. It is expected that asymmetrical tidal mixing will occur due to vertical velocity shear and horizontal eddies. From daily mean tidal flows obtained from the ADCP observation, it was found that the northwest of Gae Island have flows in NW~NE, the west of Geumo Island have the average currents of up to 21 cm/s WSW~SSW and counterclockwise circulation or eddy currents are formed in the west of Sori Island.