• The Journal of the Acoustical Society of Korea
• /
• v.36 no.2
• /
• pp.108-114
• /
• 2017

We have experimentally analyzed the self-radiation impedance of an ultrasonic transducer with a square radiation surface that is used as a vibrator in underwater ultrasonic detection systems. The radiation reactance and the radiation resistance were measured in the range from 1 to 3 of ka that is the product of a wave number and a length of the edge of the square vibrator. By comparing the measured results with those of theoretical calculation of the radiation impedance using a series, we confirmed the validity of the experimental method and experimentally confirmed the variation trend in the radiation impedance of the square radiation surface.

• The Journal of the Acoustical Society of Korea
• /
• v.19 no.7
• /
• pp.3-6
• /
• 2000

Because the generally reported radiation impedance has been calculated for vibrating surface with infinite baffle, the results have difficulties to apply for design of the real transducers with finite baffle. In this paper, with assuming a vibrating surface as a set of small point sources, a new calculation method for the vibrating surface with finite baffle is suggested by considering the effect of finite baffle on the source strength of each point source. As an example, the variation of self-radiation impedance for rectangular vibrating surface is calculated according to the size of baffle. The results show that the suggested method is useful.

• Proceedings of the Acoustical Society of Korea Conference
• /
• autumn
• /
• pp.265-268
• /
• 2000

트랜스듀서의 삽입손실과 임펄스 응답특성 등을 정확히 해석하기 위해서는 대상 주파수 대역에 대한 특성을 알아야한다. 방사임피던스는 주파수의 함수이기 때문에 이러한 특성을 결정하는 중요한 요소이다. 따라서 본 연구에서는 정방형 방사면을 가지는 트랜스듀서 이용하여, 무한배플에서의 방사임피던스를 고려한 삽입손실을 이론적으로 계산하고 무한배플로 근사할 수 있는 모델을 제작하고, 이를 실험으로 확인한 결과 좋은 일치를 보이고 있어 본 연구에서 제안한 해석법의 타당성을 확인하였다.

• The Journal of the Acoustical Society of Korea
• /
• v.19 no.7
• /
• pp.85-89
• /
• 2000

In this paper, by extending the previously developed self- and mutual-radiation impedance calculation method for a regular-square vibrating surface by using numerical series, we proposed a method to obtain the self-radiation impedance of a rectangular transducer with an arbitrary integer ratio of the length to width. The proposed method exhibits high accuracy and a short computation time. After investigating the accuracy and computation time as the number of elements changes, we have calculated the self-radiation impedance of several rectangular transducers, and compared the results with those in the literature.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.4
• /
• pp.277-284
• /
• 2018

This paper reports the transparent electrode, which would be applied to transparent displays and smart glasses. Herein, a squared metal mesh with the most widely used copper wire in microwaves is studied for the alternating thin-film-type transparent and conducting indium tin oxide(ITO), with a low conductivity(sheet resistance > $5{\Omega}/sq.$). The electromagnetic performance of a patch antenna with metal mesh is analyzed. This paper presents the results of the optical(OT, optical transparent) and electrical(sheet resistance) characteristics of a squared metal mesh, which is a basic design. To improve the OT, copper wire(w=0.2 mm) is used in fabricating the squared metal mesh and the relationship between the OT and the antenna performance(radiation gain, radiation pattern) was analyzed according to the mesh size(l=1, 2 mm). The measurement results show that the antenna performance and the optical characteristic are in inverse proportion to each other. In real applications, the optical and electrical characteristics, and the costs of production are to be considered.

• Proceedings of the Acoustical Society of Korea Conference
• /
• 1998.06e
• /
• pp.185-188
• /
• 1998

본 연구에서는 256(16$\times$16)개의 마이크로폰 정방형 배열에 의한 음향 홀로그래피 시스템을 제작하고, FFT에 의한 음향 홀로그래피법 알고리즘을 이용한 음원 위치 추정에 관하여 기술한다. 본 연구에서 설계한 측정 시스템은 방사된 음들을 동시 수음함으로서 실시간 데이터 처리가 가능하다. 또한 환경 잡음이 존재하는 실음장에서도 계측시간을 단축함과 동시에 고분해능으로 안정하게 음원의 위치를 추정할 수 있다. 본 연구의 타당성을 검증하기 위해 SYSNOISE에 의한 음장해석과 음향 홀로그래피 알고리즘을 이용하여 마이크로폰 간격 및 측정면 크기, 측정거리의 최적 조건을 구한 후 실음장 측정 실험에 적용하였다. 수치 시뮬레이션과 무향실에서 실험 데이터에 의해 음원 위치를 추정한 결과 유사한 결과를 얻었다.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.18 no.1
• /
• pp.119-127
• /
• 2018

The formal data used in the business is managed in a table form without normalization due to lack of understanding and application of data modeling. If the balance of the database design is destroyed, it affects the speed of response to the data query, and the data obesity becomes high. In this paper, it is investigated how data obesity improved through database design through optimized data modeling. The data query path was clearly visualized by square design through data modeling based on the relationship between object (data) and object, from the radial and task - oriented isolation design where data obesity is excessive. In terms of data obesity, the obesity degree of the current research support database was 57.2%, but it was 16.2% in the new research support database, and the data obesity degree was reducd by 40.5%. In addition, by minimizing redundancy of data, the database has been improved to ensure the accuracy and integrity of the data.