• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.4
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• pp.1-5
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• 1982

A new algorithm, based upon a lattice formulation, is presented for linear prediction. The output of the algorithm is the reflection coefficients that guarantee the stability of the all-pole model. The equations are derived that compute the covariance of the residuals recursively at each prediction stage, and in processing of computing that eqations, the reflection coefficients are estimated without computing the predictor coefficients. Comparing with covariance-lattice method, it can be said that the new algorithm reduce the number of computations to about half and is more efficient for fitting of the high-order model.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.36-38
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• 1994

A novel UHS relaying algorithm using reflection coefficients estimation is proposed. Based on a travelling ware approach the algorithm can determine the fault location in a travelling time of the protected lone. The discrimation of the reflected wave from others is possible observing the difference of two coefficients. The algorithm is tested using results determined by EMTP.

• The Journal of the Acoustical Society of Korea
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• v.8 no.1
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• pp.67-74
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• 1989

The reflection coefficients of the sound absorbing materials are obtained from the standing wave ratio in the standin wave tube. This method is rather laborious to find the sound pressure maximum and minimum. We devised new method for determination of the complex reflection coefficients of the materials. The sound pressures and the phases are measured at least three points along the axis of the tube. The complex reflection coefficients are determined from the measured values by least square method. The measured results for the glasswool with thickness of 5cm and density of $50kg/m^3$ and the steel plate with thickness of 1.5cm are in good agreement with those of the conventional method. It is possible to measure the complex reflection coefficients at low frequencies with short standing wave tube and to interface with the personal computer which is very useful for the handling of amount of samples.

• Journal of applied mathematics & informatics
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• v.27 no.5_6
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• pp.1017-1031
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• 2009

The problem of interaction of surface water waves by small undulation at the bottom of a laterally unbounded sea is treated on the basis of linear water wave theory for both normal and oblique incidences. Perturbation analysis is employed to obtain the first order corrections to the reflection and transmission coefficients in terms of integrals involving the shape function c(x) representing the bottom undulation. Fourier transform method and residue theorem are applied to obtain these coefficients. As an example, a patch of sinusoidal ripples is considered in both the cases as the shape function. The principal conclusion is that the reflection coefficient is oscillatory in the ratio of twice the surface wave number to the wave number of the ripples. In particular, there is a Bragg resonance between the surface waves and the ripples, which is associated with high reflection of incident wave energy. The theoretical observations are validated computationally.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.189-194
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• 2001

The present study describes the Bragg reflection of monochromatic water waves propagating over a train of doubly-sinusoidally varying topographies. A numerical model based on the boundary element method is firstly verified by calculating reflection and transmission coefficients of waves over a trench. Calculated solutions are compared with those of the eigenfunction expansion method. The model is then used to simulated reflection of monochromatic water waves propagating over doubly-sinusoidally varying bottom topographies. Obtained reflection coefficients are compared with those of available laboratory measurements, those of the eigenfunction expansion method and the extended mild-slope equation. A reasonable agreement is shown.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.3
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• pp.292-301
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• 2008

A linearized model for hysteretic acoustic nonlinearity of imperfectly joined interface is proposed and analyzed by using Coulomb damping to investigate the characteristics of the reflection and transmission coefficients for harmonic waves at the contact interface. Closed crack is modeled as non welded interface that has nonlinear discontinuity condition in displacement across its boundary. Based on the hysteretic contact stiffness of the contact interface, the reflected and transmitted waves are determined by deriving the tractions on both sides of the interface in terms of the discontinuous displacements across the interface. It is found that the amplitudes of the reflected and transmitted waves are dependent on the frequency and the hysteretic stiffness. As the frequency of the incident wave increases, the higher reflection and lower transmission are obtained. It also shows that the hysteresis of the interface increases the reflection coefficient, but reduces the transmission coefficient. A fatigue crack is also made in aluminum specimen to demonstrate these characteristics of the reflection and transmission of contact interfaces.

• Journal of Korea Water Resources Association
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• v.37 no.9
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• pp.729-736
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• 2004

Analysis of reflection of random waves propagating over rectangular submerged non-porous breakwaters was performed by using the eigenfunction expansion method. In this study, random waves were generated by superposition of several monochromatioc waves. Reflection coefficients were calculated by summing each numerical results of regular waves. Predicted results from the eigenfunction expansion method were in a good agreement with the results of laboratory measurements. Reflection coefficients of random waves were also resonated at the Bragg reflection condition.

• Geomechanics and Engineering
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• v.18 no.6
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• pp.605-614
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• 2019

The present paper seeks to investigate propagation and reflection of waves at free surfaces of homogeneous, anisotropic and rotating micropolar fibre-reinforced medium with voids. It has been observed that, in particular when P-wave is incident on the free surface, there exist four coupled reflected plane waves traveling in the medium; quasi-longitudinal displacement (qLD) wave, quasi-transverse displacement (qTD) wave, quasi-transverse microrotational wave and a wave due to voids. Normal mode Analysis usually called harmonic solution method is adopted in concomitant with Snell's laws and appropriate boundary conditions in determination of solution to the micropolar fibre reinforced modelled problem. Amplitude ratios which correspond to reflected waves in vertical and horizontal components are presented analytically. Also, the Reflection Coefficients are presented using numerical simulated results in graphical form for a particular chosen material by the help of Mathematica software. We observed that the micropolar fibre-reinforced, voids and rotational parameters have various degrees of effects to the modulation, propagation and reflection of waves in the medium. The study would have impact to micropolar fibre-reinforecd rotational-acoustic machination fields and future works about behavior of seismic waves.

• Journal of information and communication convergence engineering
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• v.14 no.3
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• pp.200-206
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• 2016

Images can be obtained by collecting rays from objects. The characteristics of electromagnetic wave propagation depend on the medium. In particular, in an underwater imaging system, the interface between air and water must be considered. Further, reflection and transmission coefficients can be found by using electromagnetic theory. Because of the fact that the values of these coefficients differ according to the media, the recorded light intensities will change. A color image sensor has three different color channels. Therefore, the reflection and transmission coefficients have to be calculated individually. Thereafter, by using these coefficients, we can compensate for the color information of underwater objects. In this paper, we present a method to compensate for the color information of underwater objects by using electromagnetic wave propagation theory. To prove our method, we conducted optical experiments and evaluated the quality of the compensated image by a metric known as mean square error.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.9
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• pp.1344-1350
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• 1990

A design method of ultra-broadband microwave amplifier is presented. A lossy network is represented as the combination of a serial impedance component and a parallel admittance component, and the realizable ranges of the gain and the reflection coefficients are derived with the components connected to the input, output or interstage network. The matching network has been designed by using the serial and parallel immittance loci which have the constant gain or reflection coefficients within the realizable ranges. Using the proposed method, deisgn examples of ultra-broadband amplifiers operating from dc to 12GHz frequency range are presented.