• 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.

• Coupled systems mechanics
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• v.10 no.2
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• pp.143-159
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• 2021

The theory of generalized thermo-magneto-electroelasticity is employed to obtain the plane wave solutions in an unbounded, homogeneous and transversely isotropic medium. Reflection phenomena of plane waves is considered at a stress free and thermally insulated surface. For incidence of a plane wave, the expressions of reflection coefficients and energy ratios for reflected waves are derived. To explore the characteristics of reflection coefficients and energy ratios, a quantitative example is set up. The half-space of the thermo-magneto-electroelastic medium is assumed to be made out of lithium niobate. The dependence of reflection coefficients and energy ratios on the angle of incidence is illustrated graphically for different values of electric, magnetic and thermal parameters.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.36-41
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• 2012

Total external reflection (TER), which does not occur on a dielectric interface, is a unique feature of surface plasmon-polaritons (SPP). We propose an SPP-TER waveguide structure consisting of low-index dielectric nanocore covered with high-index dielectric on a flat metal surface. The SPP mode confined in the nanocore by the TER effect has a mode size much smaller than wavelength scale. Numerical comparison of mode characteristics between the SPP-TER waveguides and other total-internal-reflection-based waveguides such as metal or high-index dielectric nanowires show that the SPP-TER structures can possess higher modal gain for applications of nanocavity lasers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.403-408
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• 2019

In general, the caisson having the perforated wall is used to for the purpose of reducing the wave reflection and wave overtopping. In this study, the hydraulic characteristics (reflection coefficient) of the perforated wall caisson chamber filled with aggregates (rocks) were investigated with hydraulic model tests. When the perforated wall chambers were filled with aggregates, the reflection coefficients would increase. However, it was confirmed that the rock filling method into the perforated wall chamber could secure the stability of the structures and satisfy the hydraulic characteristics at a certain level.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.3
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• pp.198-203
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• 1993

Hydraulic experiments were carried out to investigate the reflection characteristics of perforated breakwaters in regular wave conditions varying the width of wave chamber and the shape of perforated wall. It was found that the reflection coefficient of the perforated breakwater was very sensitive to the change of wave chamber width. giving its minimal value when the width of the wave chamber is approximately 0.2 times the wave length in the wave chamber. This phenomenon may be resulted from the wave resonance inside the wave chamber. The reflection coefficients slightly varied for all shapes of perforated wall. i.e., vortical slit, horizontal slit or circular hole. However, the reflection trend of the structure was not significantly affected by the shape of the perforated wall.

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.40-45
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• 2002

In this study, the effects on hydraulic characteristics are discussed as the permeable underlayer thickness of the rubble mound structure changes. A series of hydraulic experiments were performed and wave run-up, reflection and set-up were investigated. Result indicated that wave run-down was affected by the water out from the permeable underlayer during down-rush. As the thickness increased, relative wave run-up decreased.

• Journal of the Korean housing association
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• v.24 no.6
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• pp.33-40
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• 2013

Hiroshi Hara is one of the most famous architect in the history of contemporary Japanese architecture. During the 1970's beginning with the Awazu Residence (1972), he designed a series of symmetrical houses, the so called 'Reflection House'. All the houses in this period were based on the method of 'reflection' and 'inversion', which means a radical reversal of the accepted notion that houses are parts of cities. A concept of "A house within a house" is expanded to "A city within a house". The important spatial characteristics of 'Reflection House' are main internal core and valley-like spaces forming internal urban streets by bringing natural elements and the components of streetscape such as plaza, open space, context of street facades and so on. This procedure is called as embedding 'city' into 'house', Hara mentioned. This paper investigates the outline of the 'Reflection House' and analyses the completed works of housing that were based on the theory. Then in the final part of the paper, the implications of 'Reflection House' and its influence on his later works of following period will be discussed.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.5
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• pp.46-53
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• 2011

The effect of a finite substrate on the radiation characteristics of a linear 7-element array antenna positioned along the E-plane is investigated. Active reflection coefficients and average active element patterns are simulated for various substrate sizes. The E-plane radiation pattern of a fully excited array for various scan angles is correlated with the active reflection coefficient and average acitive element pattern. The effect of E-plane substrate size on the radiation characteristics of a linear array along the E-plane is larger than that of H-plane substarte size.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.2
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• pp.357-363
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• 2000

The received field strength is varied with the electrical characteristics of the reflection medium in the case of the line-of-sight. To obtain the electrical characteristics of medium, the relationship between reflection coefficients and complex dielectric constants of the medium is derived, and a equation of circle which is related to reflection coefficient and ratio of transmitted power to received one is represented. A algorithm is proposed, which is to predict the electrical characteristics of the medium by using the received field strength.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1113-1118
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• 2011

In order to evaluate the characteristics of solid-solid contact interfaces, reflection or transmission techniques involving normal-incidence longitudinal waves are generally used. However, these normal-incidence techniques are of limited use in field applications such as in the inspection of welded parts. The oblique-incidence ultrasonic technique may be an alternative for overcoming these problems. However, in this technique, the mode conversion at the contact interfaces should be taken into account along with the normal and tangential interface stiffness. In this study, we have suggested a theoretical model for obliqueincidence ultrasonic waves at the contact interfaces and analyzed their reflection and transmission characteristics. Experimental results showed that the measured reflection coefficient and second harmonic wave agreed well with the suggested theoretical model. Consequently, the oblique-incidence technique can be a promising method for evaluating the characteristics of the contact interfaces.