• 한국소음진동공학회논문집
• /
• 제24권1호
• /
• pp.21-27
• /
• 2014

In this paper, an approximate formula for radiation efficiency of the plate surround by an infinite rigid baffle is studied. The plate is simply supported and one side is in contact with air, while other side with water. By assuming an infinite plate, the fluid loading effect is derived in terms of an effective mass. Based on the observation that the fluid loading effect decreases as frequency increases, the radiation efficiency formula at high frequency, which was originally derived for a plate vibrating in the air, is modified as the approximate formula for a submerged plate. The fluid loading effect is taken into account in the wavenumber of the plate. Comparisons of the approximate formula with the numerical results shows that they match well except the mid-frequency range in which numerical results show many oscillations. In numerically solving the fully coupled equations of motion, fourfold integrals of the impedance coefficients are reduced to single nonsingular integrals, which results in substantial reduction in computing time.

• 대한전자공학회논문지
• /
• 제4권4호
• /
• pp.22-27
• /
• 1967

임의장의 두 선형안테나를 중심의 높이가 다르게 서로 평행하게 놓았을 때의 상호임피이던스의 일반적인 표시식을 얻고 이식을 특별한 경우에 대해서 적용해본 결과 다른 이들에 의해서 제시된 것에 귀착됨이 들어나 이 일반표시식의 정당성을 확인할 수 있었다. 또한 간단한 수직편파다단안테나의 경우에 대하여 윗식을 이용해서 얻은 각 상호임피이던스로 부터 여상안테나 각부의 방사성전류분포를 계산하여 보았으며 이와같은 방법이 전류분포에 대한 하나의 간이해석법이 될 수 있다는 것을 알았다.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
• /
• pp.395-400
• /
• 2002

Epoxy coating and sealing used in nuclear plants for the protection of radiation degrades with aging and hazardous atmosphere. In order to evaluate the degradation of the epoxy, dependence of the acoustic impedance on the change of mechanical properties has been used. Unlike metals, the surface of the epoxy coating on a concrete liner is so wavy that the acoustic impedance is difficult to measure by using the reflectivity of the ultrasound on the interface surface because of the irregular reflection and propagation from the epoxy surface. SA(simulated annealing) algorithm is applied to calculate the acoustic impedance using a reflection wave from the rough epoxy surface. The surface waviness and acoustic impedance are taken into account and determined by SA method to evaluate the state of degradation quantitatively.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 추계학술대회논문집
• /
• pp.155-159
• /
• 2004

In this paper, it was analyzed the characteristics of electrical and acoustical variations for loudspeaker due to fabrication processes. First, mass of each components of loudspeaker was measured by electric precision scale and performed statistical analysis. Second. Thiele-Small parameters of sample loudspeakers produced by unskilled students were identified by known mass parameter identification method using electrical impedance method and investigated on the variations of each parameter. Electrical impedance tests and acoustic frequency responses were measured on sample loudspeakers and variations were examined to grasp relationship between components variation and fabrication processes. Main factors to effect the changes of electrical impedance were concluded by fabrication processes errors not by components of loudspeaker.

• 대한전자공학회논문지
• /
• 제19권6호
• /
• pp.80-83
• /
• 1982

X-밴드 주파수에서 λg/4 개방 마이크로스트립 선로 급전형 스로트 점렬을 구현하였다. 최적 급전점은 실험적으로 결정하였고 스로트 점각의 여러 주파수에서 입력 임피던스와 복재 패턴을 측정하였으며 다소 다른 길이의 16개 소자와 본 논문에서 제시한 급전 선로를 사용하여 주파수 대역을 증가시켜 보았다. A quarter-wavelength open circuited microstripline slot array is realized at X-band froquency. The optimal feeding point is experimentally determined. The input impedance of the slot array for various frequencies and its radiation pattern are measured. The bandwidth of the slot array is increased by using the 4×4 elements which are slightly different in length and feeding network which is suggested in this papers.

• 한국정밀공학회지
• /
• 제18권9호
• /
• pp.204-209
• /
• 2001

The finite element model for automotive muffler analysis is improved by modifying the boundary condition of outlet and the mesh of finite element model. The model minimizes the difference between transmission loss from analysis and that from experiment. Four different boundary conditions and the four types of finite element model are tested to find out the best one of those. From the case study it is verified that the bevel of transmission loss can be changed by the variation of radiation impedance value. Also the resonance or anti-resonance frequencies of transmission loss can be shifted by the variation of finite element mesh. An improved finite element model of muffler is proposed in consideration with the accuracy and the computing time of analysis.

• 한국전자파학회논문지
• /
• 제10권4호
• /
• pp.636-644
• /
• 1999

상대 유전율이 2.5인 태프론 기판(31 mil)과 상대 유전율이 1.06인 Foam을 이용하여 개구 결합 급전 방식 의 Ku 밴드 U 슬롯 마이크로 스트립 안테나플 섣계 및 제착하고 반사손실, 동일/교차 편파 방사패턴. 이득 등을 측정하였다. Foam을 사용한 경우 교차편파와 후방방사를 적절한 크기 이내로 제한하는 범위 내에서 38 %정도의 임피던스 대역폭을 보였으며 시율레이션 결과와 잘 일치하였다. 동일/교차 편파 방사 패턴도 시율 레이션 결과와 유사하였다.

• Journal of electromagnetic engineering and science
• /
• 제7권3호
• /
• pp.116-121
• /
• 2007

Novel design of a wideband monopole antenna for DVB-H service is presented. The proposed antenna is designed based on a monopole antenna. It consists of folded monopole and parallel parasitic element. The folded segment of the folded monopole makes the antenna shorter. The length of the parasitic element obtains additional resonance frequencies. The gap distance between the folded monopole and the parasitic element is a key parameter to control impedance matching for wideband operation. The antenna has wide band performance, good impedance and radiation characteristics from 470 MHz to 870 MHz. The measured return loss for operating frequencies over DVB-H band is better than 10 dB. Good radiation patterns are also obtained. The measured results are compared with calculated results using Ansoft HFSS(High Frequency Structure Simulator).

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 추계 학술대회논문집(수송기계편)
• /
• pp.97-100
• /
• 2005

Precise prediction of resonance frequency has been the subject of numerous papers related to Helmholtz resonator design because of its high performance at the frequency. The resonance frequency is dependent upon not only the internal dimensions of resonator but also the external boundary conditions such as the existence of other resonators in Helmholtz resonator array panel. However, the latter effect, which changes the external end correction of resonator, has not been well studied. We propose a formula to calculate the radiation impedance (or external end correction) of Helmhoitz resonator array panel. Any distance between adjacent resonators and any angle of Incidence can be allowed in the method. Numerical examples show how and how much the distance affects the resonance frequency of the panel. It is also found that the maximum absorption of the panel varies with the resonator arrangement.

• 한국통신학회논문지
• /
• 제21권6호
• /
• pp.1587-1595
• /
• 1996

We obtained the predicted and measured results for the reflection coefficient and radiation pattern of Ka-band (20- GHz) corrugated horn, which is usually used for feeder of reflector antenna for satellite communication, using suface impedance condition. In order to predict the reture losses of corrugated horn, we analyzed propagation constant of hybrid mode in the corrugated waveguide and then obtained the total reflection coefficient using the circuti theory of multi-step transformer. We also got the radiation pattern of corrugated horn with small flare angle, considering the phase deviation and integrate transverse field on aperture. A test model of corrugated horn antenna for Ka-band designed using theory and program displayed performance and the results agree with the theoretical prediction.