• Water for future
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• v.19 no.3
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• pp.259-266
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• 1986

A numerical study of the process of wave deformation, such as reflection and transmission coefficients and wave forms with bottom change was carried out by Boundary Element Method using linear elements. It is assumed that the incident wave is normal and oblique to the bottom and the wave may be described by linear theory The accuracy of the computational scheme is investigated by comparing the results of other researchers in the following several cases. (1) Simple and sloping stepped bottom geometry (2) Submerged breakater type bottom geometry (3) Trench type bottom geometry

• Korean Journal of Optics and Photonics
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• v.25 no.5
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• pp.279-285
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• 2014

We propose an electrically controllable terahertz wave modulator based on a metamaterial and vanadium dioxide ($VO_2$) thin film. A square loop shape is designed to play the roles of both a resonating metamaterial and a heater to electrically control the conductivity of $VO_2$. The transmission characteristics of the modulator were controlled by voltage. The transmission coefficient of the modulator was stably changed from 0.27 to 0.80 at 470 GHz according to the conductivity values of $VO_2$.

• Korean Journal of Optics and Photonics
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• v.21 no.1
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• pp.33-37
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• 2010

We performed time-domain terahertz (THz) spectroscopy to determine optical constants of highly conductive carbon nanotube (CNT) films. The CNT films have been fabricated on a flexible plastic substrate by using spin-coating or vacuum filtration. We found that the transmission of THz waves can be controlled by manipulating the thickness of the films and by post-treatments. From amplitude and phase information of the transmitted THz waves, we obtain optical constants such as refractive indices and dielectric constants of the CNT films. The frequency dependent dielectric constants show good metallic behaviors, relevant to the Drude free electron models with high plasma frequencies. It is also found that the dielectric constants are higher for the acid-treated films. Finally, the frequency dependent dielectric constants which are free from substrate effects have been demonstrated by using CNT films deposited on cellulose membranes.

• Journal of the Korean Vacuum Society
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• v.9 no.3
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• pp.285-289
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• 2000

It has been well known that weak axial magnetic field on the process plasma enhances plasma density. As the magnetic field helps a specific polarized EM wave mode to penetrate into the plasma, the energy transfer to the plasma enhances and the ion density increases. We have analyzed systematic change of the dispersion relation caused by the cyclotron resonance condition. This resonance occurs at near 5 gauss to provide minimum penetration depth, as known before. RF penetration depth increases abruptly beyond the magnetic field of 5 gauss, and this phenomena lessen as the collision frequency increases.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.209-212
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• 2001

수중에서 물과 공기 다공을 갖는 다공성 매질의 주파수 및 다공율 변화에 따른 음향특성을 고찰하였다. 다공성 매질로서 원통형 다공을 인위적으로 균일하게 배열한 판형 루사이트 (Lucite)를 사용하였다. 수중에서 음파를 다공성 매질의 원통형 다공의 축 방향과 평행하게 입사하였을 때, 빠른 파 (fast wave)는 다공 내의 매질에 영향을 받지 않으나, 느린 파 (slow wave) 및 원통형 다공을 전파하는 비평면 고차 정상 모드 파 (nonplanar higher normal mode wave)는 다공 내의 매질에 크게 영향을 받는다. 3MHz부터 4MHz까지의 주파수 영역에서 전체 파 (total wave), 빠른 파 및 느린 파의 음속 및 음압투과계수를 주파수 및 물과 공기 다공율 변화에 따라 측정하였다. 비강체 다공성 매질에서의 음파 전파특성에 대한 MBA (modified Biot-Attenborough) 모델의 이론 결과와 실험결과를 비교, 분석하였다.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.133-138
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• 2000

In this paper some shapes of the FBW cross sections were examined to improve the performance of FBW for the long wave. Trapezoidal section and prominence section were examined. Linear potential theory is used and the boundary element method is use for numerical computation. Proper choice of the pontoon geometry may improve the transmission coefficient in the long wave range for a given wave period.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.53-58
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• 2016

A ray tracing method to analyze the propagation channel characteristics for a millimeter-wave indoor wireless communication system is presented. Reflected rays from planar as well as rough surfaces are included. Transmitted rays though a thin dielectric slab are considered. Maps representing received power levels and RMS delay spread from a transmitter in a rectangular room are shown. The received power levels in the empty room for bottom's roughness factors of 0 and 0.13 are represented. The simulation results are well consistent with the calculation of Friis equation with reflection coefficient. Any size of furniture the shape of plane form can be positioned anywhere in the room.

• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.3
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• pp.35-44
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• 2002

In this paper, the analytic studies on the wave control performance of moored pontoon-type floating breakwater are presented. A two-dimensional eigenfunction expansion method is adopted to study the motion responses and the transmission coefficients of pontoon-type floating breakwater in beam waves. The stiffness coefficients of mooring line are idealized as linear elastic spring. Comparison of the analytical results with a numerical results (FEM) shows good agreement over a wide range of frequencies. The performance of mooed pontoon-type floating breakwater is tested with various design parameters such as sectional geometry, mooring line characteristics and wave frequencies. It is found that the properly designed floating breakwater can be an effective wave control structure.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.2
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• pp.67-73
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• 2005

The characteristics of the floating breakwater is briefly reviewed and their performance is numerically investigated. The numerical scheme is a boundary integral method for inviscid potential flows, and various two-dimensional floating breakwater modules are studied focusing on the transmission coefficient. The general characteristics of pontoons is studied as function of mooring line stiffness, mass moment inertia and draft. Trapezoidal-, hat- and table-shape cross-sections are also studied with varying shape-parameters. The efficiency varies with changes in each shape-parameter and for some cases satisfying tranquility can be expected with even longer waves.

• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.199-204
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• 1999

As the correct measuring of the light dosimetry in biological tissues give the important affection to the effect of PDT treatment we used Monte Carlo simulation to measure the light dosimetry on this study. The parameters using in experiments are the optical properties of the real biological tissue, and we used Henyey-Greenstein phase function among the phase functions. As we results, we displayed the result the change of Fluence rate and the difference against the previous theory was at least 0.35%. Biological tissues using in experiment were Human tissue, pig tissue, rat liver tissue and rabbit muscle tissue. The most of biological tissue have big scattering coefficient in visible wavelength which influences penetration depth. The penetration depth of human tissue in visible region is 1.5~2cm. We showed that it is possible to measure fluence rate and penetration depth within the biological tissues by Monte Carlo simulation very well.