• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제4권1호
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• pp.22-30
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• 2001

A new concept wave absorber is proposed. It is a net type wave absorber. Its efficiency was reported in another publication. Since it is based on new concept, the traditional wave absorber theory is not applicable. It is modeled by introducing damping terms in linearized free surface boundary conditions in this study. The length and the thickness of the wave absorber are modeled by the length and the coefficient of the damping terms. Series of experiments are carried out to get the data for the coefficients of the damping term. The boundary element method is adopted to solve the system. The predicted wave heights show excellent agreement with those of experiments when the lengths of the incoming waves are within the length of the wave absorber.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.254-256
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• 2003

This paper presents the result if a study m the development of a net type wave absorber with air pumping. The authors already show the usefulness of net type wave absorber in the previous study. However, when it comes to the long waves, it was not easy to maintain the same efficiency with net type wave absorber only. The authors tried to overcome this difficulty by adding air bubbles to the water. The results show that combining the net type wave absorber and the air bubble is more efficient than single adoptation of the wave absorber or a net type wave absorber.

• 대한조선학회논문집
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• 제38권1호
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• pp.37-42
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• 2001

본 논문에서는 유연한 그물 구조로 된 새로운 개념의 소파 장치를 제안한다. 본 연구를 하게된 동기는 이미 알려져 있는 기존의 소파장치들이 작은 파수조에서는 제대로 그 역할을 하지 못한다는 점에서 시작되었다. 소파기의 성능을 파악하기 위하여 소파기의 길이와 소파기의 면적을 변화시켜 여러 가지 파장의 파에 대해서 실험을 수행하였다. 실험 결과 제안된 소파 장치는 그 길이가 짧은 파수조에서도 뛰어난 성능을 발휘함을 알 수 있었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 춘계학술대회 논문집
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• pp.210-214
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• 2000

This paper proposes a new wave absorber made of flexible net structures. The motivation of this research is that the wave absorbers which already invented are not effective in small wave flume. The proposed new wave absorber demonstrated its efficiency when used in small-length wave flume.

• 한국항해항만학회지
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• 제34권4호
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• pp.299-304
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• 2010

In this paper, the EM wave absorber was developed for the 94-GHz detecting radar system. To analysis an EM wave absorber in millimeter wave band, we fabricated three absorber samples using carbon black and titanium dioxide and permalloy with chlorinated polyethylene. After measuring the complex relative permittivity, the absorption characteristics are simulated by 1D FDTD according to different thicknesses of less than 1.0 mm. Then, the EM wave absorber was fabricated based on the FDTD simulation. As a result, the measured results agreed well with the simulated ones, and the developed EM wave absorber with a thickness of 0.7 mm had the desired absorption characteristics of more than 14 dB in the frequency range of the 94-GHz band.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.622-629
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• 2003

고성능 복합형 전자파 흡수체를 개발하기 위해 종래에는 지지재로서 주로 Silicone 고무나 CPE가 사용되어 왔다. 본 연구에서는 전통 공예에서 사용되어 오던 옻에 대한 전자파 흡수능을 조사하고 이를 지지재로 사용하여 MnZn 페라이트와 배합하여 전자파 흡수체를 제작한 경우의 전자파 흡수능을 조사하고, 흡수체의 두께에 따른 흡수능을 조사하였다. 옻을 지지재로 한 MnZn 페라이트 복합형 전자파 흡수체는 CPE나 Silicone 고무를 지지재로 한 전자파 흡수체에 비하여 우수한 전파흡수특성 나타내었으며, 옻의 두께 변화에 따라 정합주파수와 전파흡수능이 변화함을 알았다.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.225-228
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• 2008

There are many studies about submerged structures or porous wave absorbers to decrease damage of coast and structures. Submerged structures and porous wave absorber are decreasing energy of incoming wave by reflecting or dissipation with changing depth or with porous rubble mound. This study addresses the reflection and transmission of long wave from a trapezoidal breakwater and a vertical porous wave absorber at the same time. A systematic shape transfer is derived to determine wave reflection and transmission. And periodic solutions are matched at the slope and the front face of the absorber by assuming continuity of pressure and mass. The transmission coefficient is determined as a function of parameters describing the incoming waves, transmitting waves through the trapezoidal breakwater and the absorber characteristics.

• Journal of Advanced Marine Engineering and Technology
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• 제39권8호
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• pp.843-848
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• 2015

The objective of this study is to observe and optimize a typical ocean environment and reduce wave reflections in the wave flume. In order to generate ocean waves in the wave flume, a combination of a horizontal piston type wave generator and wave absorbers was installed in the channel. Two probes for measuring the wave heights, i.e., wave level gauges, were used to record the continuous variation of the wave surface, the phase difference, and the maximum (crest) and minimum (trough) points of the propagating waves. In order to optimize the shape and size of the propagating waves, several absorption methods were proposed. Apart from an active wave absorption method, we used methods that involved vertical porous plates, horizontal punching plates, and sloping-wall-type wave absorbers. To obtain the best propagating waves, a sloping-wall-type wave absorber was chosen and tested in terms of the constitutive filling materials and the location and shape of the plate. This study also focused on the theoretical prediction of the wave surface, separating them into the incident and reflective components. From the results, it is evident that the wave absorber comprising a hard filling material exhibits a better performance than the absorber comprising a soft material, i.e., the wave absorber can be a strong sink to control the energy of the incoming wave. In addition, larger wave absorbers correspond to lower reflectance because a larger volume can reduce the incoming wave energy. Therefore, at constant absorber conditions, the reflectance of the wave increases as the wave period increases. Finally, the reflectance of the wave was controlled to be less than 0.1 in this study so that the wave flume can be used to simulate an offshore environment.

• 전자공학회논문지A
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• 제28A권12호
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• pp.19-23
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• 1991

A method for suppressing unwanted resonance modes by attaching an electromagnetic wave absorber onto a metal case was studied to prevent performance deterioration of electronic devices. The electromagnetic wave absorber fabricated for this study had an attenuation characteristics above 20dB in the frequency band from 450MHz, 1150MHz. A rectangular cavity resonator whose resonance frequencies of TE$_{101}$, TE$_{102}$ modes were 900MHz, 1250MHz, respectively, was made to measure attenuation for the electromagnetic wave absorber-metal assembly. The result showed that the resonance mode for high attenuation was sensitive to the location of electromagnetic wave absorber, and the attenuation characteristics above 20dB could be obtained when electromagnetic wave absorber was properly positioned.

• 한국항해항만학회지
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• 제30권2호
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• pp.161-166
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• 2006

In order to construct an Anechoic Chamber satisfying international standards for EMI testing, it has been recognized that the absorption characteristics of the EM wave absorber must be higher than 20 dB over the frequency band from 30 MHz to 18 GHz. In this paper, an EM wave absorber with super wide-band frequency characteristics was proposed and designed in order to satisfy the above requirements by using the Equivalent Material Constant Method(EMCM) and Finite Difference Time Domain(FDTD). The proposed absorber is to attach a pyramidal absorber onto a hemisphere-type absorber on a cutting cone-shaped ferrite. As a result, the proposed absorber has absorption characteristics higher than 20 dB over the frequency band from 30 MHz to more than 20 GHz.