• Bulletin of the Korean Mathematical Society
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• v.54 no.4
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• pp.1111-1122
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• 2017

In this work, we consider constacyclic and cyclic self-dual codes over the rings $R_k$. We start with theoretical existence results for constacyclic and cyclic self-dual codes of any length over $R_k$ and then construct cyclic self-dual codes over $R_1={\mathbb{F}}_2+u{\mathbb{F}}_2$ of even lengths from lifts of binary cyclic self-dual codes. We classify all free cyclic self-dual codes over $R_1$ of even lengths for which non-trivial such codes exist. In particular we demonstrate that our constructions provide a counter example to a claim made by Batoul et al. in [1] and we explain why their claim fails.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.893-895
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• 2005

We represent an efficient intelligent digital redesign method for a Takagi-Sugeno (T-S) fuzzy system. intelligent digital redesign means that an existing analog fuzzy-model-based controller converts to equivalent digital counter part in the sense of state-matching. The proposed method performs previous work, moreover, it allows to matching the states of the overall closed-loop T-S fuzzy system with the predesigned analog fuzzy-model-based controller. And the problem of stability represent convex optimization problem and cast into linear matrix inequality (LMI) framework. This method applies to the helicopter systems which are the nonlinear plant and determine the feasibility and effectiveness of the proposed method.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.3105-3107
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• 2005

We represent an efficient intelligent digital redesign method for a Takagi-Sugeno (T-S) fuzzy system. Intelligent digital redesign means that an existing analog fuzzy-model-based controller converts to equivalent digital counter part in the sense of state-matching. The proposed method performs previous work, moreover, it allows to matching the states of the overall closed-loop T-S fuzzy system with the predesigned analog fuzzy-model-based controller. And the problem of stability represent convex optimization problem and cast into linear matrix inequality (LMI) framework. This method applies to the helicopter systems which are the nonlinear plant and determine the feasibility and effectiveness of the proposed method.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.493-496
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• 2006

Rarefied gas flows through two-dimensional micro channels are studied numerically for the performance optimization of a nanomembrane-based Knudsen compressor. The effects of the wall temperature distributions on the thermal transpiration flow patterns are examined. The flow has a pumping effect, and the mass flow rates through the channel are calculated. The results show that a steady one-way flow is induced for a wide range of the Knudsen number. The DSMC(direct simulation Monte Carlo) method with VHS(variable hard sphere) model and NTC(no time counter) techniques has been applied in this work to obtain numerical solutions.

• Journal of ILASS-Korea
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• v.11 no.1
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• pp.39-47
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• 2006

In-cylinder flows in a motored 3.5L four-valve SI engine were investigated quantitatively using three-component LDV system, to determine how engine configuration affects the flow field. The purpose of this work was to develop quantitative methods which correlate in-cylinder flows to engine performance. For this study, two distinct intake/piston arrangements were used to examine the flow characteristics. Quantification of the flow field was done by calculating two major parameters which are believed to characterize adequately in-cylinder motion. These quantities were turbulent kinetic energy(TKE) and tumble ratio in each plane at each crank angle. The results showed that in-cylinder flow pattern is dominated by the intake effects and two counter rotating vortices, developed during the intake stroke, produced relatively low tumble ratio. Therefore, the applicability of these quantities should be carefully considered when evaluating characteristics resulting from the complex in-cylinder flow motions.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.2
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• pp.39-45
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• 2004

Atomic Force Microscope (AFM) has been widely used in micro/nano-scale studies and applications for the last few decades. In this work, wear characteristics of silicon-based AFM tip was investigated. AFM tip shape was observed using a high resolution SEM and the wear coefficient was approximately calculated based on Archard's wear equation. It was shown that the wear coefficient of Si and ${Si}_3$$N_4$ tips were in the range of ${10}^{-1}$~${10}^{-3}$and ${10}^{-3}$~${10}^{-4}$, respectively. Also, the effect of relative humidity and sliding distance on adhesion-induced tip wear was investigated. It was found that the tip wear has more severe for harder counter surface materials. Finally, the probable wear mechanism was analyzed from the adhesive and abrasive interaction point of view.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2436-2440
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• 2009

In this work, TCO-less dye-sensitized solar cells (DSCs) using Ti-mesh layer is fabricated for high-efficient low-cost solar cell application. The Ti-mesh metal can replace TCO in the photo-electrode part of DSCs, thus the cell structure is composed of a glass/dye sensitized TiO2 particle/ Ti-mesh layer/electrolyte/Pt sputtered counter electrode/ glass. The Ti-mesh electrode with high conductivity can collect electrons from the $TiO_2$ layer and allows the ionic diffusion of $I^-/I_3^-$ through the mesh hole. Thin Ti-mesh ($\sim40{\mu}m$ in thickness) electrode material is processed using rapid prototype method. The efficiency of prepared TCO-less DSCs sample is about 1.45 % ((ff: 0.5, Voc: 0.52V, Jsc: 5.55 $mA/cm^2$).

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.65-69
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• 2005

Curretly, the development of MEMS(Micro Electronic Mechanical System) technology awakes many research's interest for the aerodynamics. This work presents the development of a compact synthetic jet actuator for flow separation control at the flat plate. The formation and evolution of fluidic actuators based on synthetic jet technology are investigated using Reynolds-Averaged Navier-Stokes equations. Also, 2-Dimensional, unsteady, incompressible Navier-Stokes equation solver with single partitioning method for Multi-Block grid to analyze and a modeled boundary condition in developed fo. the synthetic jet actuator. Both laminar and turbulent jets are investigated. Results show very good agreement with experimental measurements. A jet flow develops, even though no net mass flow is introduced. Pair of counter-rotating vortices are observed near the jet exit as are observed in the experiments.

• The KSFM Journal of Fluid Machinery
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• v.10 no.5
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• pp.27-33
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• 2007

Rarefied gas flows through two-dimensional micro channels are studied numerically for the performance optimization of a nanomembrane-based Knudsen compressor. The effects of the wall temperature distributions on the thermal transpiration flow patterns are examined. The flow has a pumping effect, and the mass flow rates through the channel are calculated. The results show that a steady one-way flow is induced for a wide range of the Knudsen number. The DSMC(direct simulation Monte Carlo) method with VHS(variable hard sphere) model and NTC(no time counter) techniques has been applied in this work to obtain numerical solutions. A critical element that drives Knudsen compressor Is the thermal transpiration membrane. The membranes are based on aerosol or machined aerogel. The aerogel is modeled as a single micro flow channel.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.2
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• pp.75-86
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• 2010

In this work the possibility of obtaining a rectilinear motion of bodies partially or totally submerged without using propellers is evaluated. The system propulsion is based on a pair of counter rotating masses that generate the thrust. The fluid-body system has been schematized in order to carry out a very simple model. Using this model an evaluation of the body motion along a longitudinal direction was performed. The motion equations of the system were written and integrated. The external forces applied to the body depend on its velocity in relation to the water. These forces were obtained by fluid dynamic simulations. Regarding the mechanical configuration suggested, the results obtained show that a certain displacement of the body along a fixed direction is obtainable.