• Steel and Composite Structures
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• v.27 no.4
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• pp.439-451
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• 2018

In the present investigation, a plane P (longitudinal) wave is made incident upon a transversely isotropic magnetothermoelastic solid slab of uniform thickness, interposed between two different semi-infinite viscoelastic solids. The transversely isotropic magnetothermoelastic sandwiched layer is homogeneous with combined effects of two temperature, rotation and Hall current in the context of GN Type-II and Type-III (1993) theory of thermoelasticity. The amplitude ratios of various reflected and refracted waves are obtained by using appropriate boundary conditions. The effect of energy dissipation on various amplitude ratios of longitudinal wave with angle of incidence are depicted graphically. Some cases of interest are also deduced from the present investigation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.957-964
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• 2011

This investigation presents a finite element method to obtain the transmission properties of bulk elastic waves in piezoelectric band gap structures(phonon crystals) for varying frequencies and modes. To this end, periodic boundary conditions are imposed on a three-dimensional model while both in-plane and out-of-plane modes are included. In particular, the mode decoupling characteristics between in-plane and out-of-plane modes are identified for each electric poling direction and the results are incorporated in the finite element modeling. Through numerical simulations, the proposed modeling method was found to be a useful, effective one for analyzing the wave characteristics of various types of piezoelectric phononic band gap structures.

• Applied Microscopy
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• v.39 no.2
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• pp.175-183
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• 2009

In this paper we present sub-50 pm resolution images of atom columns simulated with the negative of the second derivative of the exit-plane wave function (EPW). The EPW can be retrieved from a focal series reconstruction in the (high resolution) transmission electron microscopy (HRTEM). The simulated images are for Si and InAs in [114] and [116] orientations, which give about sub-50 pm separations of atom columns. The theoretical reason for the validity of this method is given from analysis based on the kinematical diffraction theory, and the limitation for applicability of this method also is discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.583-586
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• 2000

This work ethibits how susceptive the shear ultrasonic waves are to a little misoriented plies according to the angle variation of shear ultrasoic waves $0^\circ$ , $45^\circ$ and $90^\circ$. Also, it is shown that shear waves, particularly the transmission mode with the transmitter and receiver perpendicular to each other, have high sensitivity for detecting anomalies in fiber orientation and ply layup sequence that may occur in the manufacturing of composite laminates. Experimental results are agreed with modeling solutions which were based on decomposition of shear wave polarization vector as it propagates through the composite laminates. This wave appeared considerably to be sensitive to CFRP composites to the thickness direction along in-plane fibers.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.317-322
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• 2003

In this paper, we design a slow-wave bandpass filter that uses a microstrip line periodically loaded with microstrip ing resonators for WLAN(5 GHz). Unlike conventional slow-wave filters, this filter is designed to produce a narrow passband at the fundamental mode of the resonators and provide lower insertion loss than that of parallel- or cross-coupled ring bandpass filters. A PBG(Photonic Band Gap) structure patterned in the ground plane is used to suppress the spurious transmission and extend out-of-band rejections Experimental result shows that the first spurious response in the stopband of the slow-wave bandpass filter can be rejected using a PBG structure.

• Applied Microscopy
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• v.38 no.1
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• pp.63-72
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• 2008

The iterative wave-function reconstruction (IWFR) method developed by Allen et al. (2004) was reviewed with concern for its applicability. The high resolution transmission electron microscopy (HRTEM) studies of the materials such as GaAs, $YBa_2Cu_3O_7$ and $Al_2CuMg$ reported in the literature were utilized in this review. In this process the basis of validity, the limiting conditions and the information limit of this method were discussed. It was particularly noted that the phase contrast image of the exit plane wave evaluated from this method reveals not only $C_s$-corrected atomic resolution within information limit, but also strong tendency of contrast proportional to the magnitude of the atomic number of compositional atoms in a crystal.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.694-700
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• 1999

In this paper, we studied the design of power divider using the slow-wave effect of Photonic Bandgap structure, which is etched on the ground plane. The proposed PBG structure can provides the changing of the characteristic impedance of the transmission line and the group delay velocity characteristic. Therefore we can make wider width than the width of conventional transmission line and decrease the length of transmission line. We presented the application for power divider using the characteristic impedance and electrical length extracted from scattering parameter. As adding proposed defect units, the effect of defect is studied. The experimental results show good agreements with the simulated results.

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1568-1575
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• 2005

The calculation of the transmission loss of the silencers with complicated internal structures by the conventional BEM combined with the transfer matrix method is incorrect at best or impossible for 3-dimensional silencers due to its inherent plane wave assumption. On this consideration, we propose an efficient practical means to formulate algebraic overall condensed acoustic equations for the whole acoustic structure, where particle velocities on the domain interface boundaries are unknowns, and the solutions are used later to compute the overall transfer matrix elements, based on the multi-domain BEM data. The transmission loss estimation by the proposed method is tested by comparison with the experimental one on an air suction silencer with perforated internal structures installed in air compressors. The method shows its viability by presenting the reasonably consistent anticipation of the experimental result.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.832-836
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• 2008

In this study, the electromagnetic coupling problem through narrow slit in an infinite conducting screen is considered for the case that the TM polarized plane wave is incident upon the slit. This study aims at explaining the mechanism of the maximum power transmission via the resonated slit using the equivalent circuit. It is shown that the transmitted power through the slit for the case of resonance corresponds to the power normally incident upon the conducting plane of the effective width 1/pi wavelengths, irrespective of the slit width. Some similarities between the maximum power transmissions observed in both the proposed structure and narrow slit in thick conducting screen are described from the viewpoint of equivalent circuit. In addition, it is found that, when the slit is resonated, the transmitted power equal to the scattered power.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.6
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• pp.181-192
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• 2001

The power flow analysis (PFA) has been performed to analyze the vibration of coupled plates excited by a point force in an arbitrary direction. The point force generates the out-of-plane vibration associated wish flexural waves and the in-plane vibration associated with longitudinal and shear waves. The energy governing equation for each type of waves was introduced and solved to Predict the vibrational energy density and intensity generated by the out-of-plane and in-plane components of the point force in an arbitrary direction. The wave transmission approach was used to consider the mode conversion at the joint of the coupled plates. Numerical results for vibrational energy density and intensity on the coupled plates were presented. Comparison of the results by PFA with exact results showed that PFA can be an effective tool to predict the spatial variation of the vibrational energy and intensity on the coupled plates at high frequencies.