• Proceedings of the KSME Conference
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• 2003.11a
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• pp.741-746
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• 2003

The main objective of present study is to obtain information for flow characteristics, such as velocity and wall shear stress, of bifurcation in blood vessel. Branch flows for Newtonian fluids are simulated by using Fluent V.6.0. The numerical simulations are carried out for five cases divided by different values of bifurcation angle and area ratio. As a result of simulation, high wall shear stress is appeared at the bifurcated region. As increasing bifurcation angle, pressure drop is increasing. In addition, as the area is decreasing, pressure drop and wall shear stress is increasing.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.5
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• pp.196-198
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• 2002

A trench shorted anode LIGBT (TSA-LIGBT) which decreases the device area and the forward voltage drop has been proposed and verified by 2D device simulations. The trench located in the shorted anode would form the shorted anode. The simulation results show that TSA-LIGBT decrease the device area by about 20% and the forward voltage drop by over 75% compared with the conventional ones. Also the troublesome negative differential resistance (NDR) regime has been eliminated successfully in the TSA-LIGBT.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1957-1962
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• 2004

The objective of this study is to perform the numerical investigation of flow characteristics in static mixers. Simulations are carried out for mixers consisting of up to six Kenics and PPM elements placed end-to-end at an angle of $90^{\circ}$and for a range of Reynolds number($1{\leq}Re{\leq}100$). The pressure drop across a six-element Kenics mixer is computed and compared with the previous experimental correlations. The results are in good agreement with the previous correlations. The simulated flow field of Kenics mixer is extremely complex and contains regions of transverse flow that is dominated by the interaction of vortices produced by the mixer elements.

• Journal of the Korea Society for Simulation
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• v.7 no.2
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• pp.153-165
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• 1998

In the Is-95 soft handoff scheme of CDMA, there occurs a tradeoff between improving quality due to the space diversity and additional resource management like updates of the active set during soft handoffs. In addition, if a mobile terminal is alternating two adjacent cells, a well-known phenomenon called ping-ping causes the resource management to be seriously degraded. By noting that in general the probability that a user initiates additional handoffs is exponentially decreased as the user has already handed over one or more times, we present a soft handoff algorithm making use of handoff profiles of mobile terminals to improve resource utilization. In the proposed algorithm the number of handoffs made so far during the call is recorded in the mobile profile and the profile data is used for adjusting handoff parameters such as the value of add or drop threshold (T_ADD or T_DROP). Through simulations, the result of the proposed algorithm is shown to improve the handoff performance by lowering the number of handoffs while simultaneously reducing resource waste.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1953-1955
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• 1999

The effects of the local lifetime control on the characteristics of IGBT are investigated using the 2-dimensional device simulator, MEDICI. Many lumped resistive turn-off simulations are carried out to analyze the effects of the minority carrier lifetime, the width, and the position of the region with a reduced local minority carrier lifetime. As a result of these simulations, it is concluded that the on state voltage drop$(V_{CE,SAT})$ is only slightly increased while the switching behavior is greatly improved if the low lifetime region is properly set. And these results are compared with IGBTs having uniform lifetime.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.2
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• pp.170-176
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• 2008

Anti roll bar model for real time multibody vehicle dynamics model has been proposed using kinematic constraint. Anti roll bar have been modeled by kinematic relationship, and mass properties are neglected. Relative angle of torsion bar spring is computed by constraint about drop-link using Newton-Raphson iteration, and then the torque of torsion bar spring can be computed with the angle and torsion spring stiffness. Finally anti roll bar force acting on both knuckle can be calculated. To validate the proposed method, half car simulations of McPherson strut suspension and full car simulations are also carried out comparing with the ADAMS vehicle model with anti roll bar. CPU times are also measured to see the real-time capabilities of the proposed method.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.769-775
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• 2019

The tensile strength of irradiated 3C-SiC, SiC with artificial point defects, SiC with symmetric tilt grain boundaries (GBs), irradiated SiC with GBs are investigated using molecular dynamics simulations at 300 K. For an irradiated SiC sample, the tensile strength decreases with the increase of irradiation dose. The Young's modulus decreases with the increase of irradiation dose which agrees well with experiment and simulation data. For artificial point defects, the designed point defects dramatically decrease the tensile strength of SiC at low concentration. Among the point defects studied in this work, the vacancies drop the strength the most seriously. SiC symmetric tilt GBs decrease the tensile strength of pure SiC. Under irradiated condition, the tensile strengths of all SiC samples with grain boundaries decrease and converge to certain value because the structures become amorphous and the grain boundaries disappear after high dose irradiation.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.2
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• pp.58-62
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• 2005

A trench MOS barrier Schottky (TMBS) rectifier is proposed which utilizes the upper half of the trench sidewall as an active area. The proposed structure improves the forward voltage drop by 20$\%$ in comparison with the conventional one without degradation in breakdown voltage. An analytical model for the field distribution is given and compared with two-dimensional numerical simulations.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.97-103
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• 2009

A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.

• Journal of computational fluids engineering
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• v.14 no.3
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• pp.105-114
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• 2009

A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.