• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.84-87
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• 2009

Electrowetting is a versatile tool to handle tiny droplets and forms a backbone of digital microfluidics. Numerical analysis is necessary to fully understand the dynamics of electrowetting, especially in designing electrowetting-based devices, such as liquid lenses and reflective displays. We developed a numerical method to analyze the general contact-line problems, incorporating dynamic contact angle models. The method is based on the conservative level set method to capture the interface of two fluids without loss of mass. We applied the method to the analysis of spreading process of a sessile droplet for step input voltages and oscillation of the droplet for alternating input voltages in electrowetting. The result was compared with experimental data. It is shown that contact line friction significantly affects the contact line motion and the oscillation amplitude. The pinning process of contact line was well represented by including the hysteresis effect in the contact angle models.

• Geomechanics and Engineering
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• v.18 no.6
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• pp.651-659
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• 2019

The IB-SEM numerical method combines the spectral/hp element method and the rigid immersed boundary method. This method avoids the problems of low computational efficiency and errors that are caused by the re-division of the grid when the solids move. Based on the Fourier transformation and the 3D immersed boundary method, the 3D IB-SEM system was established. Then, using the open MPI and the Hamilton HPC service, the computational efficiency was increased substantially. The flows around a cylinder and a sphere were simulated by the system. The surface of the cylinder generates vortices with alternating shedding, and these vortices result in a periodic force acting on the surface of the cylinder. When the shedding vortices enter the flow field behind the cylinder, a recirculation zone is formed. Finally, the three-dimensional pore flow was successfully investigated.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.119-121
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• 1991

Multifilamentary superconducting wires exposed to an alternating field generate the coupling loss and hysteresis loss. The geometric shapes of multifilamentary superconducting wire are very complicate, and loss generating mechanism is too. In this paper, coupling loss of superconducting wire in case of twelve filament is calculated by two dimensional numerical analysis, and compared with value of conventional formulus. The basic idea of this calculating method is potential difference of external transverse field.

• Communications of the Korean Mathematical Society
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• v.23 no.4
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• pp.487-497
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• 2008

Buchsbaum and Eisenbud showed that every Gorenstein ideal of grade 3 is generated by the submaximal order pfaffians of an alternating matrix. In this paper, we describe a method for constructing a class of type 3, grade 3, perfect ideals which are not Gorenstein. We also prove that they are algebraically linked to an even type grade 3 almost complete intersection.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.109-112
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• 1996

In this paper, we composed utility interactive photovoltaic generation system of current source inverter, and controlled that low harmonic and high power factor are hold by supposing control and compensation method which is concerned with synchronous signal distortion and modulation delay. And we put parallel resonant circuit into dc link, so, magnitude of direct reactance was reduce by restraining direct current pulsation which had accumulation of pulsating power in alternating electrolytic condenser. Also we controlled that modulation factor is operated around maximum output of solar cell.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.907-909
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• 2003

We report a novel method of activation-annealing, named as induction annealing (IA). IA is realized by applying alternating electric field induced by alternatingmagnetic filed applied to the sample. We observed the enhanced kinetics of dopant activation by using IA.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1046-1048
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• 1999

This Paper compares two mathematical decomposition coordination methods to implementing the distributed optimal Power flow(OPF) using the regional decomposition: the Auxiliary Problem Principle(APP) and the Alternating Direction Method(ADM), a variant of the conventional Augmented Lagrangian approach. A case study was performed with IEEE 50-bus system.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1999.11a
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• pp.168-171
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• 1999

This paper describes the influence of conducting particle within the coaxial cylindrical electrodes gap under alternating voltage condition investigated using charge simulation method. If the conducting particles precent in the gas insulated system, they can cause decrement of breakdown voltage. Thus, three dimensions computations of electric fields and electrostatic forces have been carried out according to particle location. The results show a good agreement with those of outside country, which can offer a practical reference on the insulation design of domestic GIS.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1073-1077
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• 1996

This paper presents a recoil and counter recoil(R&CR) motion measurement method using linear variable differential transformers(LVDT). The output of a LVDT is obtained from the differential voltage of the 2nd transformers. As a sensor core is attached at the motion body, the output is directly proportional to the core motion. Displacement, velocity and acceleration are measure from the core length. With a comparison between the measurement result and the known value which is obtained by the precision steel tape, the accuracy and the usefulness of the proposed scheme is validated.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.59-64
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• 2002

In this paper, the preconditioned multistage time stepping methods which are popular multigrid smoothers is implemented for the compressible Navier-Stokes calculation with full-coarsening multigrid method. The convergence characteristic of the point-Jacobi and Alternating direction line Jacobi(DDADI) preconditioners are studied. The performance of 2nd order upwind numerical fluxes such as 2nd order upwind TVD scheme and MUSCL-type linear reconstruction scheme are compared in the inviscid and viscous turbulent flow caculations.