• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.263-266
• /
• 2004

This paper describes an intelligent piezoelectric traffic sensor which can be detected the over-weighted vehicles In motion. Based on finite element analysis for the sensor, the sensitivity was analyzed and the design was optimized. Studied parameters are the material properties of constitutional parts, the geometry of the sensor, the weight of the vehicle, and the speed of the vehicle. To verify the simulated results, we manufactured the sensor having the optimized geometry and the sensitivity was measured in the range from 0.5 to 3 ton of tensile and compressive stress. The measured results shows that the sensitivity and linearity of the sensor are closely agree with the designed values.

• Proceedings of the Acoustical Society of Korea Conference
• /
• autumn
• /
• pp.369-370
• /
• 2004

초음파의 조차에 의한 인체내부의 온도상승의 측도로 열지수(thermal index)가 사용되고 있으며, 이는 주파수 및 음향파워에 의존한다. 초음파 조사에 의한 인체내부의 온도상승을 평가하는데 사용되는 재료를 조직 모사 물질이라 한다. 본 논문아사는 단위 음향파워에 대한 온도 변화인 열 감도(thermal sensitivity)를 새로이 정의하였으며, 이 물리량으로 조직모사물질의 성능을 평가 할 수 있다는 것을 제안하고자 한다.

• The Journal of the Acoustical Society of Korea
• /
• v.8 no.1
• /
• pp.31-37
• /
• 1989

The effectiveness of using a composite beam with constrained visco-elastic layer as a dynamic vibration absorber is investigated. The performance of this absorber is evaluated in terms of displacement transmissibility when to a primary beam with built-in ends and compared to that of the uniform beam absorber. The results of analysis and design show that it is possible to suppress simultaneoulsy the peak transmissibilities at two or more resonance frequencies and the optimal parameters are located within the available viscoelastic material properties.

• The Journal of the Acoustical Society of Korea
• /
• v.18 no.8
• /
• pp.25-31
• /
• 1999

This paper describes design and fabrication of a new bi-directional ultrasonic linear motor working by means of a traveling wave. With the finite element method, we design and verify validity of the new structure, and determine its optimal structure, material, size, and boundary conditions for proper generation of the traveling wave. Based on the results, a prototype of the motor has been fabricated and characterized, which thereby proves practical applicability of the new structure.

• The Journal of the Acoustical Society of Korea
• /
• v.13 no.1E
• /
• pp.5-10
• /
• 1994

It is obtained the general expessions of the numerical method are applied for the TEM-mode analysis of multu-layer multi-coupled microstrip lines, In this paper, coupled microstrip are replaced by three-coupled microstrip lines in special aplications. Three-layer versions of three-coupled microstrip lines are specially attactive because of the additional flexibilities offered by three-layer configuration. This structure can be used for obtaining large capacitance and preventing coupling among microstrip lines in filter and coupler. Sappihre is chosen for anisotropic substrates material. The permittivity parallel to the optical axis is higher than the permittivity in the plane perpendicular to this axis.

• The Journal of the Acoustical Society of Korea
• /
• v.5 no.2
• /
• pp.39-47
• /
• 1986

흡음 계수는 흡음재의 흡음 특성을 제시해 주는 기본적 물리량이다. 본 연구에서는 일반적으로 흡음재로 사용되는 흡음재의 흡음 특성을 알기 위해 두께 18mm, 직경 105mm인 10종의 흡음재를 택하 여 흡음재의 흡음 계수를 구하였다. 이를 위해 impedance tube를 제작하여 관내에 흡음재를 넣은 후 관 내에 만들어진 정상파의 최대 음압과 최소음압의 비, 정상파비를 이용하여 흡음 계수를 구했다. 그 결과 흡음재의 흡음 특성은 진동수, 흡음재으 lwowlf, 두께 및 다공성에 크게 의존해 스폰지, 유리 섬유 등의 흡음 효과가 좋게 나타났으며 특히 같은 두께의 동일 흡음재일지라도 흡음재 뒷면의 공기층을 적절리 조절함으로써 특정 진동수 근처에서의 흡음 효과를 증대시킬 수 있었다.

• The Journal of the Acoustical Society of Korea
• /
• v.18 no.4E
• /
• pp.3-9
• /
• 1999

Deep-water sonar transducers of FFR (Free Flooded Ring) type have been designed using a coupled FE-BEM. The proposed sonar transducers are composed of piezoelectric ceramic tubes and structural steel materials for simple fabrication. In order to have an omnidirectional beam pattern around 30kHz, a conic steel is placed below a piezoelectric tube or a steel disc is placed between two piezoelectric tubes. The dynamics of the sonar transducer is modelled in three dimensions and is analyzed with external electrical excitation conditions. Various results are available such as directivity patterns and transmitting voltage responses. The most optimal structure and dimensions of the steel material were calculated, so that the beam patterns of the sonar transducers had +/- 3dB omnidirectivity at 30kHz.

• The Journal of the Acoustical Society of Korea
• /
• v.14 no.2E
• /
• pp.12-18
• /
• 1995

Capactive miro pressure sensor is simulated with finite element methods to analyze the effect of geometrical variation on its performace. Sensor material is th silicon single crystal. The sensor consists of a disk type diaphragm and several bridges connected to a rigid frame. Structural variables in consideration are the thickness of the diaphragm and the bridges, radius of the circular plate, and the number of bridges. Results of static, dynamic and sensitivity analyses reveal the best structure of the sensor among the fifteen cases under investigation.

• The Journal of the Acoustical Society of Korea
• /
• v.31 no.4
• /
• pp.253-259
• /
• 2012

Goldingham's measurement of the velocity of sound undertaken in the early nineteenth century was the first large-scale measuring enterprise which considered various meteorological factors such as temperature, humidity, atmospheric pressure, the direction of the wind, etc. Goldingham's successful performance of measuring the velocity of sound by employing the sounds of cannons as sound source in Madras (now Chennai), a colonial region of India, for one and a half years was supported by material, institutional and social resources. As the official astronomer at the Madras Observatory, he was benefitted by the undemanding employment of accurate measuring instruments under the support of the Madras Army enabled him to gain reliable data and his reputation as professional experimentalist facilitated the acknowledgment of their trustworthiness.

• The Journal of the Acoustical Society of Korea
• /
• v.28 no.7
• /
• pp.618-629
• /
• 2009

The MPEG-4 Audio Lossless Coding (ALS) standard belongs to the family MPEG-4 audio coding standards. In contrast to lossy codecs such as AAC, which merely strive to preserve the subjective audio quality, lossless coding preserves every single bit of the original audio data. The ALS core codec is based on forward-adaptive linear prediction, which combines remarkable compression with low complexity. Additional features include long-term prediction, multichannel coding, and compression of floating-point audio material. This paper describes the basic elements of the ALS codec with a focus on prediction, entropy coding, and related tools and points out the most important applications of this standardized lossless audio format.