• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.16 no.3
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• pp.205-216
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• 2012

When it comes to Lorentz symmetry violation, there are generally two approaches to studying noncommutative field theory: 1) conventional fields are equivalent to noncommutative fields; however, symmetry groups are larger. 2) The symmetry group is the same as conventional standard model's symmetry group; but fields here are written based on the Seiberg-Witten map. Here by adopting the first approach, we aim to connect Lorentz violation coefficients with noncommutative parameters and compare the results with the second approach's results. Through the experimental values obtained for the Lorentz-violating parameters, we obtain a limit of noncommutative symmetry.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.148-153
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• 2001

A computational investigation of the effect of the electromagnetic force(or Lorentz force) on the flow behavior around a circular cylinder, a typical model of bluff bodies, is conducted. Two-dimensional unsteady flow computation for $Re=10^2$ is carried out using a numerical method of finite difference approximation in a curvilinear body-fitted coordinate system by solving the momentum equations including the Lorentz force as a body force. The effect of the spatial variations of the Lorentz forcing region and forcing direction along the cylinder circumference is investigated. The numerical results show that the Lorentz force can effectively suppress the flow separation and oscillation of the lift force of the circular cylinder cross-flow, leading to the reduction of the drag.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.38-39
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• 2005

A new C-aperture is needed in the Ag film because general metal films don't alternate with the PEC film. In this paper, using FDTD method and the Drude-Lorentz metal model, a new C-aperture is designed in the Ag film and the 40nm-beam size and the $7\%$ near-field transmission efficiency are obtained at 28nm distance from the aperture. Its near-field transmission is about 1000 times larger than that of a 54 nm${\times}$54 nm square aperture.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.41-46
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• 2008

This paper conducts the research on the variation in the characteristics of the resonance and impedance of the metallic parallel plates due to the replacement of the normal dielectric substrate by the metamaterial. The ENG(${\epsilon}<0$), MNG(${\mu}<0}$) and DNG(${\epsilon},{\mu}<0$) types of metamaterial as well as the DPS(Double Positive) material are taken into consideration a full-wave modal analysis method known for accurate computation, as the SRR-kind of Lorentz model for permittivity and metal wire-periodic array-kind of Drude model for permeability, and the behaviors of parallel plates' resonance mode and impedance are observed. Based upon the observation, the design guidelines for the substrate can be addressed regrading how to suppress the parallel plates' spurious resonance modes that degrade the quality of the electronic equipment.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.38-38
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• 2008

• Journal of The Korean Association For Science Education
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• v.27 no.2
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• pp.126-133
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• 2007

The 'Science and Technology Mania' award program is an annual nationwide award activity organized to provide teenagers with opportunities for engaging in a high-technology-based long-term project work. The task involves designing a model ship propelled by the Lorentz force (a Lorentz ship) that allows diverse approaches irreducible to one right answer, and thus adopts features of science and technology in-the-making, In this study, we attend to opportunities for learning science that the uncertain aspects of artifact-designing project provide with participants, particularly when students communicate with scientists about their design practices. We analyze oral presentation sessions of the program and articulate two findings. First, students articulate embodied knowing in the presence of scientists. Second, students enact discursive resources deployed in concrete action. We conclude that students' design practices constitute referent that communication is directed toward and therefore become resources for developing scientific discourse.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.220-222
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• 2006

This paper presents intelligent digital redesign method of global approach for hybrid state space fuzzy-model-based controllers. For effectiveness and stabilization of continuous-time uncertain nonlinear systems under discrete-time controller, Takagi-Sugeno(TS) fuzzy model is used to represent the complex system. And global approach design problems viewed as a convex optimization problem that we minimize the error of the norm bounds between nonlinearly interpolated lineal operators to be matched. Also, by using the bilinear and inverse bilinear approximation method, we analyzed nonlinear system's uncertain parts more precisely. When a sampling period is sufficiently small, the conversion of a continuous-time structured uncertain nonlinear system to an equivalent discrete-time system have proper reason. Sufficiently conditions for the global state-matching of the digitally controlled system are formulated in terms of linear matrix inequalities (LMIs). Finally, a T-S fuzzy model for the chaotic Lorentz system is used as an example to guarantee the stability and effectiveness of the proposed method.

• Transactions of Materials Processing
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• v.21 no.7
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• pp.441-446
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• 2012

A sequential coupled field analysis of electromagnetic free bulging was performed by using FEM. A 2D axi-symmetric electromagnetic model based on the magnetic vector potential is proposed for the calculation of magnetic field and Lorentz's forces. The Newmark integration method is used to calculate the transient dynamic plastic deformation of sheet during free bulging. In the finite element model, the effect of sheet deformation on the electromagnetic field analysis is taken into consideration. In order to confirm the sequential electromagnetic-mechanical coupling analysis, an experiment with an electromagnetic forming apparatus was conducted. The results showed that the final bulge height of the sheet predicted from the proposed method is in good agreement with experimentally measured height.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.283-287
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• 2005

The slow evolution of global magnetic fields and other dynamical processes in atmospheres of CP magnetic stars lead to the development of induced electric currents in all conductive atmospheric layers. The Lorentz force, which results from the interaction between a magnetic field and the induced currents, may modify the atmospheric structure and provide insight into the formation and evolution of stellar magnetic fields. This modification of the pressure-temperature structure influences the formation of absorption spectral features producing characteristic rotational variability of some spectral lines, especially the Balmer lines (Valyavin et al., 2004 and references therein). In order to study these theoretical predictions we began systematic spectroscopic survey of Balmer line variability in spectra of brightest CP magnetic stars. Here we present the first results of the program. A0p star $\Theta$ Aur revealed significant variability of the Balmer profiles during the star's rotation. Character of this variablity corresponds to that classified by Kroll (1989) as a result of an impact of significant Lorentz force. From the obtained data we estimate that amplitudes of the variation at H$\alpha$, H$\beta$, H$\gamma$ and H$\delta$ profiles reach up to $2.4\%$during full rotation cycle of the star. Using computation of our model atmospheres (Valyavin et al., 2004) we interpret these data within the framework of the simplest model of the evolution of global magnetic fields in chemically peculiar stars. Assuming that the field is represented by a dipole, we estimate the characteristic e.m.f. induced by the field decay electric current (and the Lorentz force as the result) on the order of $E {\~} 10^{-11}$ cgs units, which may indicate very fast (< < $10^{10}$ years) evolution rate of the field. This result strongly contradicts the theoretical point of view that global stellar magnetic fields of CP stars are fossil and their the characteristic decay time of about $10^{10}$ yr. Alternatively, we briefly discuss concurring effects (like the ambipolar diffusion) which may also lead to significant atmospheric currents producing the observable Lorentz force.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.11a
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• pp.95-98
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• 2005

This paper presents intelligent digital redesign method of global approach for hybrid state space fuzzy-model-based controllers. For effectiveness and stabilization of continuous-time uncertain nonlinear systems under discrete-time controller, Takagi-Sugeno(TS) fuzzy model is used to represent the complex system. And global approach design problems viewed as a convex optimization problem that we minimize the error of the norm bounds between nonlinearly interpolated linear operators to be matched. Also by using the power series, we analyzed nonlinear system's uncertain parts more precisely. When a sampling period is sufficiently small, the conversion of a continuous-time structured uncertain nonlinear system to an equivalent discrete -time system have proper reason. Sufficiently conditions for the global state -matching of the digitally controlled system are formulated in terms of linear matrix inequalities (LMls). Finally, we prove the effectiveness and stabilization of the proposed intelligent digital redesign method by applying the chaotic Lorentz system.