• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.9
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• pp.715-721
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• 2013

Minimization techniques are adaptations of Helical structure, Meta material, multi-layer structure etc. But, Helical structure is not suited to minimization technique of RF circuit having single resonant frequency. Because it generate resonant frequency following as rotation of circumference. Meta material and multi layer structure have weakness of expenditure and complex structure. In addition, conventional three dimensional M$\ddot{o}$bius Strip and planar M$\ddot{o}$bius Strip are not two dimensional planar M$\ddot{o}$bius Strip that has weakness of electrical coupling effect. Therefore, in this paper, we proposed miniaturized and reduced electrical coupling effect antenna by adaptation of Quasi M$\ddot{o}$bius Strip that topology is same as three dimensional M$\ddot{o}$bius Strip with Via-Hole structure. According to the simulation result, physical circumferential length is 1/3 minimized compared with conventional ring antenna under the same resonant frequency. In addition, coupling effect is not nearly generates near to the resonant frequency, 2.4GHz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.674-679
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• 2005

This paper is concerned with the application of perturbation method to the dynamic analysis of space structure floating in space. In dealing with the dynamics of space structure, the use of Lagrange's equations of motion in terms of quasi-coordinates were suggested to derive hybrid equations of motion for rigid-body translations and elastic vibrations. The perturbation method is then applied to the hybrid equations of motion along with discretization by means of admissible functions. This process is very tiresome. Recently, a new approach that applies the perturbation method to the Lagrange's equations directly was proposed and applied to the two-dimensional floating structure. In this paper, we propose the application of the perturbation method to the Lagrange's equations of motion in terms of quasi-coordinates. Theoretical derivations show the efficacy of the proposed method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.5
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• pp.942-948
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• 2011

This paper deals with characteristic analysis of axial flux permanent magnet (AFPM) machines with axially magnetized PM rotor using quasi-3-D analysis modeling. On the basis of magnetic vector potential and a two-dimensional (2-D) polar-coordinate system, the magnetic field solutions due to various PM rotors are obtained. In particular, 3-D problem, that is, the reduction of magnetic fields near outer and inner radius of the PM is solved by introducing a special function for radial position. And then, the analytical solutions for back-emf and torque are also derived from magnetic field solutions. The predictions are shown in good agreement with those obtained from 3-D finite element analyses (FEA). Finally, it can be judged that analytical solutions for electromagnetic quantities presented in this paper are very useful for the AFPM machines in terms of following items : initial design, sensitivity analysis with design parameters, and estimation of control parameters.

• Fibers and Polymers
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• v.2 no.1
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• pp.140-143
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• 2001

To better understand the formation of necking in drawing processes of fibers, strain distributions during drawing processes have been analyzed. For simplicity, one-dimensional incompressible steady flow at a constant temperature was assumed and quasi-static model was used. To describe mechanical properties of solid polymers, non-linear visco-plastic material properties were assumed using the power law type hardening and rate-sensitive equation. The effects of various parameters on the neck formation were matematically analyzed. As material property parameters, strain-hardening parameter, visco-elastic coefficient and strain-rate sensitivity were considered and, for process parameters, the drawing ratio and the process length were considered. It was found that rate-insensitive materials do not reach a steady flow state and the rate-sensitivity plays a key role to have a steady flow. Also, the neck formation is mainly affected by material properties, especially for the quasi-static model. If the process length changes, the strain distribution was found to be proportionally re-distributed along the process line by the factor of the total length change.

• Steel and Composite Structures
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• v.17 no.3
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• pp.305-320
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• 2014

The lowest critical value of the compressive force acting in the plane of symmetrically laminated quasi-isotropic thin rectangular plates is investigated. The critical buckling loads of plates with different types of lamination and aspect ratios are parametrically calculated. Finite Differences Method (FDM) and Galerkin Method are used to solve the governing differential equation for Classical Laminated Plate Theory (CLPT). The results calculated are compared with those obtained by the software ANSYS employing Finite Elements Method (FEM). The results of Galerkin Method (GM) are closer to FEM results than those of FDM. In this study, the primary aim is to conduct a parametrical performance analysis of proper plates that is typically conducted at preliminary structural design stage of composite vessels. Non-dimensional values of critical buckling loads are also provided for practical use for designers.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.9 s.102
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• pp.1030-1036
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• 2005

This paper is concerned with the application of perturbation method to the dynamic analysis of space structure floating in space. In dealing with the dynamics of space structure, the use of Lagrange's equations of motion in terms of quasi-coordinates were suggested to derive hybrid equations of motion for rigid-body translations and elastic vibrations. The perturbation method is then applied to the hybrid equations of motion along with discretization by means of admissible functions. This process is very tiresome. Recently, a new approach that applies the perturbation method to the Lagrange's equations directly was proposed and applied to the two-dimensional floating structure. In this paper. we propose the application of the perturbation method to the Lagrange's equations of motion in terms of quasi-coordinates. Theoretical derivations show the efficacy of the proposed method.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.E2
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• pp.75-81
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• 2003

Variational data assimilation, which is recently introduced to the air quality modeling, is a promising tool for obtaining optimal estimates of initial conditions and other important parameters such as emission and deposition rates. In this paper. two advanced techniques for variational data assimilation, based on the adjoint and quasi-inverse methods, are tested for a simple air quality problem. The four-dimensional variational assimilation (4D-Var) requires to run an adjoint model to provide the gradient information in an iterative minimization process, whereas the inverse 3D-Var (I3D-Var) seeks for optimal initial conditions directly by running a quasi -inverse model. For a process with small dissipation, I3D-Vu outperforms 4D-Var in both computing time and accuracy. Hybrid application which combines I3D-Var and standard 4D-Var is also suggested for efficient data assimilation in air quality problems.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.2
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• pp.133-142
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• 2004

In this article, the constitutive relations of three types of piezoelectric benders, which are a unimorph bender, a bimorph bender and a triple-layer bender, are derived based on the beam theory under the quasi-static equilibrium condition. The relation coefficients are described as the geometry and material properties of the benders. More general constitutive relations involving fixed-free, fixed-roll, and fixed-simply supported boundary conditions under the inconsistent length condition between the piezoelectric layer and the nonpiezoelectric one are discussed. The complicated constitutive relations can be easily calculated and checked by using the symbolic function in ‘Mathematica’. The relation coefficients for the benders are plotted in three dimensional graph using the developed program.

• Structural Monitoring and Maintenance
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• v.6 no.3
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• pp.191-218
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• 2019

The aim of the present investigation is to examine the propagation of plane waves in transversely isotropic homogeneous magneto thermoelastic rotating medium with fractional order heat transfer. It is found that, for two dimensional assumed model, there exist three types of coupled longitudinal waves (quasi-longitudinal, quasi-transverse and quasi-thermal waves). The wave characteristics such as phase velocity, attenuation coefficients, specific loss, penetration depths, energy ratios and amplitude ratios of various reflected and transmitted waves are computed and depicted graphically. The conservation of energy at the free surface is verified. The effects of rotation and fractional order parameter by varying different values are represented graphically.

• Advances in materials Research
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• v.9 no.4
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• pp.289-309
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• 2020

The aim of the present investigation is to examine the propagation of plane harmonic waves in transversely isotropic homogeneous magneto visco thermoelastic rotating medium with fractional order heat transfer and two temperature. It is found that, for two dimensional assumed model, there exist three types of coupled longitudinal waves (quasi-longitudinal, quasi-transverse and quasi-thermal) in frequency domain. phase velocities, specific loss, penetration depth, attenuation coefficients of various reflected waves are computed and depicted graphically. The effects of viscosity and fractional order parameter by varying different values are represented graphically.