• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.930-937
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• 2011

The characteristics of mean velocity and turbulence have been analyzed in the circular open channel flow using PIV measurement data for a wide range of water depth. The measured data are fitted to a velocity distribution function over the whole depth of the open channel. Reynolds shear stress and mean velocity in wall unit are compared with the analytic models for fully-developed turbulent boundary layer. Both the mean velocity and Reynolds shear stress have different distributions from the two-dimensional boundary layer flow when the water depth increases over 50% since the influence of the side wall penetrates more deeply into the free surface. The cross-stream Reynolds normal stress also has considerably different distribution in view of its peak value and decreasing rate in the outer region whether the water depth is higher than 50% or not.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.897-900
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• 2005

RF linearity of double-gate MOSFETs is investigated using accurate two-dimensional simulations. The linearity has been analyzed using the Talyor series. Transconductance is dominant nonlinear source of CMOS. It is shown that DGMOSFET linearity can be improved by a careful optimization of channel thickness, gate oxide thickness, gate length, overlap length and channel doping concentration. The minimum $P_{IP3}$ data are compared in each case. It is shown that DG-MOSFET linearity can be improved by a careful optimization of channel thickness, gate oxide thickness, gate length, overlap length and channel doping concentration..

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.480-484
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• 2000

The channel length influence of n-channel Si-based FETs is investigated by computer simulation. Using a two-dimensional hydrodynamic model, devices having various gate length are examined. We have observed the characteristics of LDD model of MOSFET by investigating of their current, voltage, electric field and impact ionization. These devices are scaled using various factors. We have analyzed I-V characteristics and the effect of impact ionization according to channel length.

• Transactions on Electrical and Electronic Materials
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• v.8 no.1
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• pp.21-25
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• 2007

A two-dimensional TCAD MEDICI simulator was used to examine the voltage transfer characteristics, on-off switching properties and latch-up of a CMOS inverter as a function of the n-channel length and doping levels. The channel in a LDMOSFET encloses a junction-type source and is believed to be an important parameter for determining the circuit operation of a CMOS inverter. The digital logic levels of the output and input voltages were analyzed from the transfer curves and circuit operation. The high and low logic levels of the input voltage showed a strong dependency on the channel length, while the lateral substrate resistance from a latch-up path in the CMOS inverter was comparable to that of a typical CMOS inverter with a guard ring.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.228-233
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• 2005

Two-dimensional Stokes flows through a micro channel with a couple of symmetric vertical fins are investigated. At far up- and down-stream from the fins, the plane Poiseuille flow exists in the channel. The slip boundary conditions are applied to take account of the Knudsen number effects. For the analysis, the method of eigen function expansion and collocation method are employed. By the results, the streamline patterns and pressure distributions are shown and the force exerted on the fin and the excess pressure drop due to the fins are determined as functions of the length of the fin and Knudsen number. It may be conjectured that the force and the excess pressure drop are almost independent of the Knudsen number.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.3
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• pp.211-221
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• 1982

Numerical analysis has been made on the heat transfer of two dimensional turbulent channel with a slat type blockage. Especially the effects of the height of slat and Reynolds number on the heat transfer characteristics of channel wall have been investigated. The methods of accelerating the convergence of the numerical solution of governing differential equation have been also examined. Line-by-line iterative method shows higher convergence rate than point-by-point iterative method for solution of both momentum equation and energy equation. The results show that the ratio of heat transfer coefficient of the wall near the blockage to that of the fully developed flow increase with increasing the ratio of blockage to channel height and decreasing the Reynolds number. These trends of variation of heat transfer coefficient with respect to the height of slat and Reynolds number agree with those of Sparrow's experiment on the pipe flow with slat type blockage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.10
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• pp.1034-1040
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• 2004

The latch-up current and switching characteristics of MOS-Controlled Thyristor(MCT) are studied with variation of the channel length and impurity concentration. The proposed MCT power device has the lateral structure and P-epitaxial layer in substrate. Two dimensional MEDICI simulator is used to study the latch-up current and forward voltage-drop from the characteristics of I-V and the switching characteristics with variation of impurity concentration. The channel length and impurity concentration of the proposed MCT power device show the strong affect on the anode current and turn-off time. The increase of impurity concentration in P and N channels is found to give the increase of latch-up current and forward voltage-drop.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.3
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• pp.461-472
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• 1995

The interaction of laminar mixed convection and surface radiation in a two-dimensional channel with an array of rectangular blocks is analyzed numerically. Three blocks are maintained at high temperature and the other bottom and top horizontal walls are insulated. Discrete ordinate method(DOM) is introduced to analyze the radiative heat transfer. The effects of the variations of Reynolds number and channel specifications on the heat transfer characteristics are investigated. The average Nusselt numbers along the block surfaces are correlated and presented in terms of Reynolds number and dimensionless geometric parameters such as the block spacing, height and channel spacing. For the conditions considered in this study, average Nusselt numbers along the block surfaces are strongly influenced by the channel spacing and Reynolds number but weakly influenced by the block spacing and block height.

• Advances in aircraft and spacecraft science
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• v.6 no.1
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• pp.19-30
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• 2019

Two- and three-dimensional turbulent airflows in a 9-degrees-bent channel are studied numerically. The inner surfaces of upper and lower walls are parallel to each other upstream and downstream of the bend section. The free stream is supersonic, whereas the flow at the channel exit is either supersonic or subsonic depending on the given backpressure. Solutions of the Reynolds-averaged Navier-Stokes equations are obtained with a finite-volume solver ANSYS CFX. The solutions reveal instability of formed shock waves and a flow hysteresis in considerable bands of the free-stream Mach number at zero and negative angles of attack. The instability is caused by an interaction of shocks with the expansion flow formed over the convex bend of lower wall.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1528-1533
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• 2004

A numerical investigation is made of transient evolutionary prcocess of electroosmotic flow in a two-dimensional microchannel connected to a reservoir. The channel height is very small so that two electric double layers forming on the charged surfaces are overlapped. Transient transports of ions in the electrolyte solution are computed by integrating the Nernst-Planck equation together with the Poisson equation for electric potential. The numerical results illustrate that there are two distinct transient phases. The physical mechanisms and relevant time scales for the transient evolution are described.