• Title/Summary/Keyword: Vertical reflection

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An Analysis of Electric-field Density into Mountain Area Using DTED (디지털 지도를 이용한 산악지형의 전계강도 분석)

  • Lim, Joong-Soo;Chae, Gyoo-Soo;Park, Young-Chul;Kim, Min-Nyum
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.7 no.5
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    • pp.852-857
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    • 2006
  • This paper presents a precision method to calculate the electric field density of mountain area using digital terrain elevation data(DTED). Generally we calculate the electric field density of a point adding a direct field density and horizontal reflection field density between two points. In this paper, we consider a vertical reflection field density from vertical surface near the wave propagation line between transmitter and receiver. The vertical reflection electric field have different propagation path and polarization from a horizontal reflection field. And the total electric field density adding horizontal field density and vertical reflection value is more accurate than a direct path electrical field density or direct field density adding a horizontal reflection field density.

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On an Analysis of Reflection and Transmission Coefficients by a Vertical Slit Plate (직립 슬릿판에 의한 반사율과 투과율 해석)

  • 조일형;김남형
    • Journal of Ocean Engineering and Technology
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    • v.16 no.3
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    • pp.1-7
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    • 2002
  • In this paper, a numerical model to analyze the performance of a vertical slit-type wave absorber is developed under the assumption of inviscid water waves. The formulation combines the linear potential theory with a semi-empirical description of the eddy-shedding at a slit-type wave absorber. We investigated the reflection coefficients over a wide frequency range for a vertical slit-type wave absorber both with and without a solid rear wall. Model test was conducted at KRISO' s two dimensional wave tank to validate the theoretical results. It is found that the agreement between theoretical results and experimental data is surprisingly good. We found that the wave absorbing system using a vertical slit plate has sufficient potentials for breakwaters for ocean development.

Estimating the Thickness Errors in Vertical-Cavity Surface-Emitting Laser Structures from Optical Reflection spectra (반사 스펙트럼을 이용한 VCSEL 에피층의 두께 오차 평가)

  • 김남길;김상배
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.40 no.8
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    • pp.572-579
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    • 2003
  • By comparing the measured optical reflection spectra with calculated one by the transfer-matrix method (TMM) in epitaxial wafers for vertical-cavity surface-emitting lasers (VCSELs), we have estimated the systematic thickness errors in a simple and nondestructive way. The experimentally confirmed technique is based on the finding that the shape of the reflection spectra depends mainly on a newly defined single parameter, the effective error in the n-mirror layers, and the thickness error in the active cavity simply shifts the Fabry-Perot resonance wavelength. Also shown is that the proposed method is reliable when the relative standard deviation of the random thickness errors is less than 0.005. Because reflection spectra are routinely measured, we can easily estimate the thickness errors nondestructively with high spatial resolution.

The Influence of Slit Shape on the Reflective Characteristic of Caissons in Harbor (항만구조물 반사특성에 미치는 Slit 형상의 영향)

  • Kim, Kyu-Han;Kim, Min-Soo;Lee, Kang-Chul;Ryu, Moo-Eun
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2006.11a
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    • pp.461-464
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    • 2006
  • The caisson of the inner wall type has a weak point that reflecting wave is big. Therefore it has been studied that the research of the decreasing reflecting wave using installation the perforated wall in front of caisson to decrease of that weak point. In this study, we analyzed the characteristic of reflection horizontal and diamond style vertical slit caisson using hydraulic model test. According to the results of experiments, we could confirm that diamond style vertical caisson has a reflection coefficient which has lower than horizontal caisson of the reflection coefficient of 5~10%.

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Enhanceement of Vertical Resolution of GPR data through Signature Deconvolution (신호파형 역대합을 통한 지중레이다 자료의 수직해상도 향상)

  • Kim, Gi-Yeong;Son, Ho-Ung;Lee, Ju-Han;Hong, Myeong-Ho
    • Journal of the Korean Geophysical Society
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    • v.9 no.1
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    • pp.1-6
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    • 2006
  • To remove ringing and increase vertical resolution of GRP data, signature deconvolution was applied to GPR data obtained using a 100 MHz antenna in the Soyang Lake. The signature was extracted through stacking reflection signals from the lake bottom. Results of this deterministic deconvolution was compared with those from the conventional Wienner method. Due to increased vertical resolution, both deconvolution methods are able to resolve three or more layers in an apparent single layer on the input data. However, identification of reflection boundaries from ringing is not easy due to poor definition in the output data of the Wienner filter. On the contrary, the signature deconvolution greatly enhances both vertical resolution and definition of reflection boundaries, showing detailed internal stratigraphic features of the three sedimentary layers. Since extraction of signature at various depths is possible, this deconvolution method can be appled effectively to unstationary GPR data.

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Effects of Wave Dissipation with Circular Cylinders (원형파일군에 의한 파랑제어 특성)

  • Lee, Seong-Dae;Kim, Seong-Deuk
    • Journal of Ocean Engineering and Technology
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    • v.22 no.4
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    • pp.27-33
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    • 2008
  • One of the central problems in astudy of the coastal surface wave environment is predicting the transformation of waves as they propagate toward the shore. The transformation is mainly due to the existence of obstacles, such as breakwaters and vertical cylinders. In general, the types of wave transformation can be classified as follows: wave diffraction, reflection, transmission, scattering, radiation, et al. This research dealtwith wave transmission and dissipation problems for two dimensional irregular waves and vertical circular cylinders. Using the unsteady mild slope equation, a numerical model was developed to calculate the reflection and transmission of regular waves from a multiple-row circular breakwater and vertical cylinders. In addition, hydraulic model experiments were conducted with different values for the properties between tire piles and the opening ratio (distances) between the rows of the breakwater. It was found that the transmission coefficients decreased with a decrease in the opening ratio and an increase in the rows of vertical cylinders. A comparison between the results of hydraulic and numerical experiments showed reasonable agreement.

Reflection Characteristics of Vortical Slit Caisson Breakwater (종 SLIT형 케이슨 방파제의 반사특성)

  • 이종인;조지훈
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.13 no.4
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    • pp.263-272
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    • 2001
  • Recently, some attempts to construct slit caisson-type breakwaters are made in Korea. Since slit caisson-type breakwaters are suitable for relatively deep sea areas, a lot of theoretical and experimental researches have been performed. In this study, the reflection characteristics of vertical slit caisson breakwaters are investigated based on the measured data in two-dimensional hydraulic model tests with irregular waves. The experiments were conducted for various cases; variation of porosity of perforated-wall, width of wave chamber, number of slits for single-and double-chamber, respectively. It is found that in the case when the wave steepness (H/L$_{s}$ ) is small, the reflection coefficients are large. The existing researches have shown that the wave reflection is minimized when the nondimensional width of wave chamber B/L is about 0.2~0.25 for the regular waves. However, for the irregular waves the reflection is lowest when $B/L_2$, is 0.13~0.15. For a same porosity condition, the wave dissipation is stronger as the width of s1it is larger. The double-chamber caisson is superior to single- chamber caisson in the wave dissipating effects.

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Reflection and Hydraulic Characteristics inside Two-Chamber Vertical Slit Caisson in 3-D Oblique Wave Field (3차원 경사입사파동장에서 이중유공슬릿케이슨 내부의 수리특성 및 반사특성)

  • Hur, Dong-Soo;Lee, Jun;Lee, Woo-Dong
    • Journal of Ocean Engineering and Technology
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    • v.28 no.3
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    • pp.227-235
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    • 2014
  • Using a 3-D numerical scheme (LES-WASS-3D) that considered wave-structure-sandy seabed interactions in a 3-D wave field, we analyzed the wave reflection and hydraulic characteristics inside a slit caisson with two chambers in a 3-D oblique wave field. To verify the 3-D numerical analysis method suggested in this study, we compared the numerical results with existing experimental results and found good agreement. The numerical analysis revealed that a standing wave field is generated on the front side of the slit caisson due to the effect of wave reflection. For incident waves propagating perpendicular to the slit caisson, the nodes and anti-nodes of the standing wave are apparent and symmetrical. However, in an oblique wave field, as the incident wave angle decreases, the nodes and anti-nodes of the standing wave become ambiguous and unsymmetrical. It was also found that the wave reflection coefficient decreases as the incident wave angle decreases. It can be pointed out that as the incident wave angle decreases, the turbulent intensity in the chamber increases. Thereby, the increased wave energy dissipation by the increased turbulent intensity reduces the rate of wave reflection. In addition, a strong turbulent intensity generally occurs in the first chamber.

Study about Anti-Reflection Coating Design and Characteristic of Laser Diode (Laser Diode의 무반사코팅 설계 및 특성에 관한 연구)

  • Ki, Hyun-Chul;Kim, Hyo-Jin;Kim, Hwe-Jong;Han, Hee-Jong;Gu, Hal-Bon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.424-425
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    • 2007
  • Anti-Reflection and High-reflection coating on the facet of semiconductor laser diode. To prevent internal feedback from both facets for realizing super luminescent diode and reducing the reflection-induced intensity noise of laser diode. Anti-Reflection coating Film was designed by Macleod Simulator. Coating Materials were decided $Ti_3O_5$ and $SiO_2$. Thickness of Coating layer $Ti_3O_5/SiO_2$ were 105[nm], 165[nm]. In the study Anti-Reflection coating Film was design for Laser diode and deposited by Ion-Assisted Deposition system. Then manufactured thin film measured electrical properties(L-I-V, Se, Resistor) and Optical properties(wavelength FFP). Slop-efficiency and FFP characteristic is 0.302[W/A], $22.3^{\circ}$(Horizontal), $24.4^{\circ}$(Vertical).

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Experimental Study for Wave Reflection of Partially Perforated Caisson by Slit Shape of Front Wall (부분 유공케이슨의 Slit 형상에 따른 반사특성 실험)

  • Lee, Jong-In
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.4
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    • pp.1455-1462
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    • 2013
  • This study examines the reflection of a partially perforated wall with single chamber by 2D and 3D hydraulic experiments. The effects of slit shape on the front wall, relative chamber width and wave steepness were discussed. For the normal incident wave condition, the reflections of horizontal slit case were lower than that of the vertical slit with the similar porosity, but the differences are not significant. When the wave steepness is relatively small, the reflection coefficients are large. In the oblique incidence, the normalized wave heights along a perforated wall with similar porosity are almost same for the vertical and horizontal slit walls and therefore the difference by slit shape can be ignored.