• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.196-202
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• 2007

In this paper, The TE(transverse electric) scattering problems by a resistive strip grating over a grounded dielectric plane with edge boundary condition are analyzed by applying the FGMM(Fourier-Galerkin Moment Method) known as a numerical procedure. For a TE scattering problem, the induced surface current density is expected to the zero value at both edges of the resistive strip, then the induced surface current density on the resistive strip is expanded in a series of the multiplication of Gegenbauer(Ultraspherical) polynomials with the first order and functions of appropriate edge boundary condition. To verify the validity of the proposed method, the numerical results of normalized reflected power for the uniform resistivity R = 100 ohms/square and R = 0 as a conductive strip case show in good agreement with those in the existing papers.

• Composites Research
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• v.16 no.5
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• pp.21-27
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• 2003

Using the theory of linear piezoelectricity, the dynamic response of a central crack in a functionally graded piezoelectric ceramic under anti-plane shear impact is analyzed. We assume that the properties of the functionally graded piezoelectric material vary continuously along the thickness. By using the Laplace and Fourier transform, the problem is reduced to two pairs of dual integral equations and then into Fredholm integral equations of the second kind. Numerical values on the dynamic stress intensity factors are presented to show the dependence of the gradient of material properties and electric loading.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.289-296
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• 2001

We propose a method to add phase-modulation to binary amplitude data pages using a twisted-nematic liquid crystal display as a dynamic phase mask. For this, the phase modulation characteristics of the display were examined both theoretically and experimentally, and an unexpected abnormal phenomenon was found experimentally in which the modulation property changed as the incident beam intensity increased. To investigate the characteristics of holographically storing the binary data images, eight pages of holograms were stored at one spot of in un-thick Dupont's photopolymer with angle multiplexing. When phase-modulation-added pages were stored at the Fourier plane, the uniformity of the signal beam at the plane was improved, and thus more holograms can be recorded with our method, compared with the conventional case of using only binary amplitude modulation under the same condition.

• Structural Engineering and Mechanics
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• v.85 no.2
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• pp.247-263
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• 2023

The paper deals with the study of the mechanical time-harmonic forced vibration of the hydro-piezoelectric system consisting of the piezoelectric plate and compressible viscous fluid with finite depth. The exact equations of motion of the theory of linear electro-elasticity for piezoelectric materials are employed for describing the plate motion, however, the fluid flow is described by employing the linearized Navier-Stokes equations for a compressible (barotropic) viscous fluid. The plane-strain state in the plate and the plane flow of the fluid are considered and the corresponding mathematical problems are solved by employing the Fourier transform with respect to the space coordinate which is on the coordinate axis directed along the platelying direction. The expressions of the corresponding Fourier transform are determined analytically, however, the inverse transforms are found numerically. Numerical results on the interface pressure and the electrical potential are obtained for various PZT materials and these results are discussed. According to these results, in particular, it is established that the electromechanical coupling effect can significantly decrease the interface pressure.

• Journal of KSNVE
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• v.4 no.3
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• pp.295-305
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• 1994

The reflection coefficient of a material at oblique incidence is measured in a free field. The sound pressure distributions are measured at discrete points on two measurement lines and then decomposed into plane wave components by using spatial Fourier transform. The inciedent and reflected plane wave components are obtained from a set of "decomposition equations" of which uses the plane wave propagation theory. Numerical simulations and experiments have been performed to see the effect of finite size of measurement area. To reduce this effect, a window fuction has been performed to see the effects of finite size of mesurement area. To reduce this effect, a window function has been proposed and its effect on the measurement of sound absorbing material property has been studied as well. The reflection coefficient obtained by this method is compared with those obtained from other methods; 2-microphone method in a duct and an expirical equation of which determines the characteristic impedance .rho.c and propagation constant k of a material from flow resistance information.formation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.170-180
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• 1995

A parallel crack in bonded dissimilar orthotropic planes under out-of-plane loading is analyzed. The problem is formulated by Fourier integral transforms, and reduced to a pair of dual integral equations. By solving the integral equations, the asymptotic stress and displacement fields near the crack tip are determined in closed form, from which the stress intensity factor and energy release rate are obtained. Discontinuity in the stress intensity factor as the distance ratio h/a of the parallel crack approaches zero is found, while the energy releas rate is shown to be continuous at h/a = 0. This information can immediately be used to generate the stress intensity factor for the parallel crack near the interface. By employing "the maximum energy release rate criterion", it could be shown in the case of no existing crack initially that the parallel crack is formed far from the interface for the more compliant material, while it is formed close to the interface for the stiffer material. material.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.3
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• pp.162-168
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• 2006

Speckle interferometry with phase-shifting method has been applied to measurement of micro-scale displacement through optical signal processing. Four-step phase-shifting method by PZT is used to measure out-of-plane displacement in spot-welded cantilever and results of optical experiments are comparable to those of FEM. Phase-shifting method using Fourier transform by PZT is applied to measurement of in-plane displacement on rectangular steel plate with a circular hole. The results of optical experiment agree well with theoretical calculation. New phase-shifting method in speckle interferometry has been implemented with a quarter wave plate. In-plane displacement of specimen is measured by the new phase-shifting method. Results of optical experiment show that the quarter wave plate can be used for phase-shifting method that is cheap and easy to use in speckle interferometry.

• Journal of Mechanical Science and Technology
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• v.18 no.3
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• pp.419-431
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• 2004

The dynamic response of a cracked functionally graded piezoelectric material (FGPM) under transient anti-plane shear mechanical and in-plane electrical loads is investigated in the present paper. It is assumed that the electroelastic material properties of the FGPM vary smoothly in the form of an exponential function along the thickness of the strip. The analysis is conducted on the basis of the unified (or natural) crack boundary condition which is related to the ellipsoidal crack parameters. By using the Laplace and Fourier transforms, the problem is reduced to the solutions of Fredholm integral equations of the second kind. Numerical results for the stress intensity factor and crack sliding displacement are presented to show the influences of the elliptic crack parameters, the electric field, FGPM gradation, crack length, and electromechanical coupling coefficient.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.246-250
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• 2015

In this paper, Timoshenko and Euler-Bernoulli beam theories(EB-beam) are used, and Fast Fourier Transformation(FFT) analysis is then employed to extract their natural frequencies using both analytical approach and Co-rotational plane beam(CR-beam) EDISON program. EB-beam is used to analyze a spring-mass system with a single degree of freedom. Sinusoidal force with various frequencies and constant magnitude are applied to tip of each beam. After the oscillatory tip response is observed in EB-beam, it decreases and finally converges to the so-called 'steady-state.' The decreasing rate of the tip deflection with respect to time is reduced when the forcing frequency is increased. Although the tip deflection is found to be independent of the excitation frequency, it turns out that time to reach the steady state response is dependent on the forcing frequency.

• Korean Journal of Optics and Photonics
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• v.3 no.1
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• pp.16-19
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• 1992

The Fourier transform spectra of a grating have been employed to determine the refractive index of a simple lens. The shearing interferometric technique is used for collimation testing of the expanded laser beam and for determining the exact focal plane. The slit attached to micro X-Y translator has been used to measure the distance between two sucessive diffraction orders in the back focal plane of the test lens. The experimental equipment is described and results are presented.