• 제어로봇시스템학회논문지
• /
• 제22권9호
• /
• pp.723-732
• /
• 2016

This paper proposes an approach to fused navigation of an unmanned surface vehicle(USV) and to detection of the outlier or interference of global positioning system(GPS). The method fuses available sensor measurements through extended Kalman filter(EKF) to find the location and attitude of the USV. The method uses error covariance of EKF for detection of GPS outlier or interference. When outlier or interference of the GPS is detected, the method excludes GPS data from navigation process. The measurements to be fused for the navigation are GPS, acceleration, angular rate, magnetic field, linear velocity, range and bearing to acoustic beacons. The method is tested through simulated data and measurement data produced through ground navigation. The results show that the method detects GPS outlier or interference as well as the GPS recovery, which frees navigation from the problem of GPS abnormality.

• Advances in aircraft and spacecraft science
• /
• 제5권2호
• /
• pp.277-294
• /
• 2018

In the space industry, structures undergo several vibration and acoustic tests in order to verify their design and give confidence that they will survive the launch and other critical in-orbit dynamic scenarios. At component level, vibration tests are conducted with the aim to reach local or global interface loads without exceeding the design loads. So, it is often necessary to control and limit the input based on a load criterion. This means the test engineer should be able to assess the interface loads, even when load cannot be measured. This paper presents various approaches to evaluate interface loads using measured accelerations and by referring to mass operators. Various methods, from curve fitting techniques to finite element-based methods are presented. The methods are compared using signals with known imperfection to identify strengths and weaknesses of each mass operator definition.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 제5회 학술대회 논문집 일렉트렛트 및 응용기술연구회
• /
• pp.29-32
• /
• 2003

Recently, the development of diagnosis technique with high confidence is important on power equipment, for this reason is to use for measurement and analysis of PD with prior appearance of insulation breakdown In this paper, we presents the analysis of trouble signal to use both method of general analysis of $\Phi$-Q-N in PD and statistical parameter by this interpretation Equipment of simulation has made independently DS for 170kV GIS of one phase with same on field. The detected signal through the sensor of Induction and Acoustic Emission is classified which used to characteristic neural network algorithm and then it is analysis.

• 한국정밀공학회지
• /
• 제9권2호
• /
• pp.122-127
• /
• 1992

In this study, we investigated defects of graphite by three NDT methods which are ultrasonic testing at 5 MHz, micro-forused X-ray testing and AE testing. As the detection of AE signals generated from graphite tensile specimens, we calculated location of AE sources and compared them with UT and X-ray test results in detecting defects of several specimens, Acoustic emission testing could be applied to some graphites which have fine grains of a few tens of micrometer, but it was difficult to those in lager grain of few fo milimeter. Also, we could understand what kind of defects has affected on tensile fracture of graphite.

• 한국자동차공학회논문집
• /
• 제8권4호
• /
• pp.85-92
• /
• 2000

The pulsating pressure waves are composed of fundamental frequency and higher order harmonics in exhaust pipe of engines. The nonlinearity in exhaust pipe is caused by their interactions. The error which is between prediction and measurement is induced by the nonlinearity. We can not explain this phenomenon using linear acoustic theory which is existing theory. So power spectrum which was used in linear theory is not useful. Bispectrum and bicoherence functions which are a higher order spectrum are applicable to explain this phenomenon. This paper proposes a nonlinear effect of pulsating pressure waves. The phenomenon proposed here is identified by using of higher order spectrum density functions.

• 음성과학
• /
• 제9권3호
• /
• pp.211-221
• /
• 2002

The prosody can play a crucial role in differentiating ambiguous sentences to correctly reflect their intended syntactic structures. In what way do the speakers in Tokyo and Sendai dialects of Japanese use prosodic elements to differentiate syntactic ambiguities? Acoustic measurement was made of utterances of ambiguous sentences in Japanese to observe prosodic strategies for disambiguation. Materials were sentences of the type ADV-VP1-NP-VP2, ADV-NP1-NP2-VP2, where the ambiguity lies in locative adverbial modification, ADV modifying either VP1 or VP2. For this construction the Japanese create the same ambiguities. After defining the depth of a syntactic boundary, F0 of the phrase before and after the boundary, and duration of the syllable and pause before the boundary were measured. The results show that Tokyo dialects speakers use F0 after syntactic boundary, and Sendai dialects speakers use of the syllable and/or pause before the boundary.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 추계학술대회논문집
• /
• pp.1104-1108
• /
• 2007

Automobile sunroof buffeting is the tonal noise of low frequency around 20Hz. It occurs due to the acoustic feedback process between the shear layer detached from the leading edge of sunroof opening and the Helmholtz resonator-like property of a car cabin. In this paper, PIV visualization technique is applied to the unsteady flow field around sunroof opening of an SUV in the full-scale automotive wind tunnel in order to find out buffeting mechanism. A phase-marking PIV measurement method, in which image and sound pressure are recorded simultaneously, and a phase-rearrangement post-processing program were developed for capturing noise-related velocity fields without expensive synchronization systems. Through this study, some characteristics of the real-car sunroof shear layers under various deflector conditions were identified and these results can provide insights into the noise reduction mechanism of the tube-type deflector.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2009년도 학술발표회 초록집
• /
• pp.1850-1854
• /
• 2009

금강하구언 상류에 위치한 규암 지점은 배수영향을 받는 지점으로 2007년도에 ADVM (Acoustic Doppler Velocity Meter)방식 자동유량측정시설을 설치하여 운영 중에 있다. 본 연구에서는 규암 지점 자동유량측정 시설에서 측정된 유량측정성과를 분석하고 다양한 방법을 통해 이를 검증하였다. 그 결과 기존 수위-유량관 계곡선식으로 방류영향 지역의 유량변화를 잘 나타낸 결과를 보였으며, 유량의 경우 총 67회 측정한 검증자료와 평균오차 7.2%로 대체로 비슷하게 산정되었으며, 금강하구언의 방류량과 갑문개방기간 동안 규암 지점의 총 유출량을 비교한 결과 3.2%의 오차를 보여 규암 지점 자동유량측정시설의 측정결과에 큰 신뢰도를 보였다.

• International Journal of Automotive Technology
• /
• 제5권4호
• /
• pp.303-309
• /
• 2004

In this paper, an interfacial crack length has been detected by using the ultrasonic attenuation coefficient on the adhesively bonded double-cantilever beam (DCB) joints. The correlations between energy release rates which were investigated by experimental measurement, the boundary element method (BEM) and Ripling's equation are compared with each other. The experimental results show that the interfacial crack length for the ultrasonic attenuation coefficient and energy release rate increases proportionally. From the experimental results, we propose a method to detect the interfacial crack length by using the ultrasonic attenuation coefficient and discuss it.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 2004년도 추계학술발표대회논문집 제23권 2호
• /
• pp.505-506
• /
• 2004

이어폰과 헤드폰의 성능 향상을 위해서는 특성에 대한 정확한 측정과 평가가 요구된다. 이어폰과 헤드폰은 room 과 같은 acoustic channel 을 거치지 않고 청취자의 귀에 직접 소리가 전달되며 ear canal 특성이 포함되기 때문에 스피커와는 다른 기준이 필요하다. 그러나 사람 귀의 canal 특성은 개인에 따른 편차가 심하여 정확한 측정 및 성능 평가에 어려움이 따른다. 본 논문에서는 이어폰과 헤드폰의 특성을 측정하는 적절한 방법을 고찰하고 측정된 데이터를 이용하여 음질 성능을 평가할 수 있는 객관적인 방법을 제시하고자 한다.