• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.4
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• pp.351-358
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• 2002

To determine a scattering performance of a rectangular waveguide with two skewed conducting posts in approximation by the mode matching method and the generalized scattering method is presented in this paper. We determined the optimized result from effective analysis to select the adequate eigenmode number in mode matching method for the skewed two conducting posts. And we obtained the scattering performance of the junction of the waveguide to coaxial line with two skewed conducting posts by application of above method. By this result, it can be seen that the transmission performance at output port of waveguide to coaxial line is 3 ㏈ at the angle, 50°And we obtained the reflection performance to decrease linearly along the skewed angle at input port.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4A
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• pp.256-266
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• 2003

In this paper, scattering characteristics of the rectangular waveguide with elliptical conducting post and equivalent impedance of post are analyzed by mode matching method and generalized scattering method. The scattcring characteristics of rectangular waveguide are varied by the height and eccentricity of elliptical conducting post. When the height of post(2.54mm, 4mm) is small, variation in scattering characteristics appears in total simulated frequency. But as the height of post(7.62mm, 9mm) is increased, it is dominant in higher frequency. The simulated result shows good agreement with the HFSS's result. Proposed structure and analysis method are easily applied to the design and manufacture of waveguide component with elliptical conducting post.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.191-194
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• 2004

본 연구에서는 해양의 기초 생산자인 잘피 (Zostera marina)의 후방산란 특성을 일주기 동안 관측 하였다. 해상 실험은 2004년 2월 $25\~29$일 기간 중 남해 동대만에서 실시 하였다. 그랩(Grab)을 이용하여 해초지의 입도를 분석 하였으며 주파수별 산란 특성을 고려하기 위해서 17, 30, 50, 80, 100, 그리고 120kHz 음원을 해초지에 수직 지향하여 주, 야간 잘피의 후방 산란을 측정하였다. 실험 환경 분석을 위해 파고와 조석 및 잘피의 생체량(biomass)측정을 실시 하였다. 광합성 시 해초지에서 발생되는 산소 공기는 해수에 의해 용존 되거나 산소 가스 형태로 존재하게 된다. 이들 공기 방울에 의해서 형성되는 공기 방울 층은 음 세기의 감쇠를 야기 시킨다. 실험 결과 주, 야간 동안 음의 산란 강도 변화를 확인 하였다.

• 한국지구과학회:학술대회논문집
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• 2010.04a
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• pp.133-133
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• 2010

인공위성 SAR센서는 기존 산란계 해상풍 자료의 낮은 해상도로 인한 여러 한계를 극복함으로써 다양한 해양연구에 있어 필요성과 활용영역이 넓어지고 있다. 이러한 추세에 따라 전세계적으로 다파장 SAR 센서들이 운용 또는 발사 예정에 있음에도 불구하고 현재까지 한반도 주변해에 대한 SAR 해상풍 산출 연구는 C밴드에만 한정되어왔다. 본 연구에서는 L밴드 해상풍 추출알고리즘을 적용하여 L밴드 SAR 영상으로부터 한반도 주변해의 해상풍을 추출하고 산란계 해상풍 자료와 비교 분석을 통해 정확도 특성을 제시하고자 하였다. 2007년 8월 우리나라 동해 지역을 관측한 L밴드 ALOS PALSAR 영상에 대해 L밴드 HH편광 GMF 알고리즘을 적용하여 해상풍을 산출하였다. 산출 해상풍은 동일시점의 산란계 QuikSCAT 자료와 공간적으로 유사한 패턴을 보였으며 두 자료 간의 풍속오차는 3.45m/s로 나타났다. 연구 해역과 같이 강한 바람 범위에서는 산출 해상풍 간의 차이가 크게 나타나며 풍향으로 인한 오차특성이 보인다. 특히 풍속의 경우, 산란계 해상풍이 중간바람 범위에 집중된 것에 비해 L밴드 SAR 산출 해상풍은 강한 바람 범위까지 포함하는 넓은 풍속값 범위를 나타냈다.

• The Journal of the Acoustical Society of Korea
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• v.20 no.1
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• pp.68-76
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• 2001

Sonar is the system that detects objects and finds their location in water by using the echo ranging technique. In order to have excellent performance in variable environment, acoustic characteristics of this system must be analyzed accurately. In this paper, based on the finite element analysis, modeling and analysis of acoustic characteristics of underwater acoustic sensors are preformed. Couplings between piezoelectric and elastic materials, and fluid and structure systems associated with the modeling of piezoelectric underwater acoustic sensors are formulated. In the finite element modeling of unbounded acoustic fluid, IWEE (Infinite Eave Envelop Element) is adopted to take into account the infinite domain. When an incidence wave excites the surface of Tonpilz underwater acoustic sensor, the scattered wave on the sensor is founded by satisfying the radiation condition at the artificial boundary approximately. Based on this scattering analysis, the electrical response of the underwater acoustic sensor under incidence, so called RVS (Receiving Voltage Signal) is founded accurately. This will devote to design Sonar systems accurately.

• The Journal of the Acoustical Society of Korea
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• v.24 no.8
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• pp.441-446
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• 2005

This paper presents the changes of acoustic scattering pattern from a single cylinder and two identical cylinders in both theoretical calculations and experimental measurements. Bi-static scattering pattern by single cylinder and two parallel cylinders (length 2m, radius 30mm) was measured in $5m\times5m\times5m$ water tank using high frequency projector (120 kHz) and hydrophone. The results show similar agreement between experiment and theory. In case of single cylinder scattering. omni-directional pattern was observed in backward but there are fluctuations or target strength in forward. Interference between each cylinder's scattering fields produce fluctuations of target strength in all directions of two cylinders.

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.257-260
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• 2006

본 연구에서는 SIR-C MLC 영상자료와 환경부에서 제공하는 중분류 토지피복도 자료를 참조하여 식생피복지역으로 예상되는 논, 밭 지역으로 분류된 농업지역과 활엽수림, 침엽수림, 혼효림 지역으로 분류된 산림지역에 대한 산란특성을 고찰하기 위해 편광 반응특성을 측정하였다. 편광반응특성분석결과 농업지역과 산림지역의 거동형태는 구형 산란체나 편평한 면에서의 거동특성을 나타냈으며, 측정된 HH, VV, HV 편광매개변수의 후방산란계수 값들은 각각의 지역에서 다른 경향을 보였다.

• Radiation Oncology Journal
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• v.19 no.1
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• pp.74-80
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• 2001

Purpose : Irradiation cones by using backscatter electrons are made for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and Materials : Backscatter electrons are produced from the primary electron beams from the linear accelerators. The design consists of a cylindrical cone that has a thick circular plate of high atomic number medium (Pb or Cu) attached to the distal end, and the plate can be adjusted the reflected angle. Primary electrons strike the metal plate perpendicularly and produce backscatter electrons that reflect through the lateral hole for treatment. Using film and a parallel plate ion chamber, backscatter electron dose characteristics are measured. Results : The depth dose characteristic of the backscatter electron is very similar to that of the hard x-ray beam that is commonly used for the intracavitary and superficial lesions. The basckscatter electron energy is nearly constant and effectively about 1.5 MeV from the clinical megavoltage beams. The backscatter electron dose rate of $35\~85\;cGy/min$ could be achieved from modern accelerators without any modification. and the depth in water of $50\%$ depth dose from backscatter electron located at 6mm for $45^{\circ}$ angled lead scatter. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusions : The measured data for backscatter electron energy, depth dose flatness dose rate and absolute dose indicates that the backscatter electrons are suitable for clinical use.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.06a
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• pp.15-18
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• 2003

Most numerical techniques such as FEM, BEM, and MOM are able to analize electromagnetic scattering problems from arbitrary shapes. Although these methods could be applied to compute electromagnetic scattering problems in frequency domain, it was limited for electrodynamic problem in time domain. In this paper, electromagnetic scattering problem from Fresnel zone plate lens are considered. Some numerical results computed by TLM are compared with Kirchhoff's approximation and PO method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.231-236
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• 2017

The space harmonics generated by a plane-wave incident upon a multi-layered dielectric grating can undergo strong resonance scattering variations known as GMR(guided-mode resonance). To clarify these effects, we examine the field propagation and dispersion curve inside the grating region by using a rigorous equivalent transmission-line theory(RETT). The results show that, at the peak of a scattering resonance, the reflected mode is almost identical to a leaky wave that can be supported by the grating structure. Thus, we confirm and generalize previous research that has occurred GMR effect associated with the free-resonant character of leaky waves at multi-layered dielectric gratings. Quantitative simulation results illustrating the behavior of typical gratings are given, and the special case of normal incidence is discussed for TM mode.