• 한국산업융합학회 논문집
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• 제4권2호
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• pp.127-132
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• 2001

In turning, the chip may be produced in the form of continuous chip or discontinuous chip. The continuous chips are dangerous to the operator and difficult to be handled at high speed machining. The signal of AE(Acoustic Emission) is found out to be related to cutting conditions, tool materials, test conditions and tool geometry in turning. In this study, the relationship between AE signal and chip form was experimentally investigated. The experimental results show that the types of chip form are possible to be classified from the AE signal using fuzzy logic.

• 한국정밀공학회지
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• 제12권3호
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• pp.130-143
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• 1995

This paper presents a new methodology for on-line tool breadage detection by sensor fusion of an acoustic emission (AE) sensor and a built-in force sensor. A built-in piezoelectric force sensor, instead of a tool dynamometer, was used to measure the cutting force without altering the machine tool dynamics. The sensor was inserted in the tool turret housing of an NC lathe. FEM analysis was carried out to locate the most sensitive position for the sensor. A burst of AE signal was used as a triggering signal to inspect the cutting force. A sighificant drop of cutting force was utilized to detect tool breakage. The algorithm was implemented on a DSP board for in-process tool breakage detection. Experiental works showed an excellent monitoring capability of the proposed tool breakage detection system.

• 한국음향학회지
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• 제34권1호
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• pp.20-35
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• 2015

수중음향 전달채널의 임펄스 응답(Channel Impulse Response: CIR)은 음속구조(Sound Speed Profile: SSP)의 영향을 받으며, 채널 임펄스 응답의 변화는 수중음향통신 시스템의 성능에 중요한 영향을 미친다. 음속분포의 변화는 단기간 내에서도 나타날 수 있으며, 수중음향 모뎀 설계 시 반드시 고려되어야 한다. 이 논문은 2013년도에 제주도 동방해역에서 수행된 JACE13에서 취득된 데이터를 기반으로 음선전달 수치해석을 통해 단기간 동안 시간에 따라 변화하는 음속구조가 음향 신호 전달에 미치는 영향을 통계적으로 분석한 결과를 제시한다. 분석결과 송 수신기 수심별로 채널 임펄스 응답의 변화가 다양하게 나타나며, 송 수신기 수심이 깊을수록 음속구조의 변동에 따른 음향신호 전달 양상의 변화는 작아지고, 신호 준위가 높게 나타난다. 이 연구에서의 다양한 거리, 송, 수신기 수심에 따라 얻어진 채널 임펄스 응답 추정 결과는 수온약층에서의 하방굴절로 인한 연속된 해저면 반사와 작은 해저면 반사손실이 장거리 신호 전파에 중요한 요인이 될 수 있음을 보여주며, 시변동성을 갖는 해양환경에서의 수중 음향 통신은 시간에 따라서 성능이 충분히 달라질 수 있다는 것을 보여준다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.170-174
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• 1999

In order to analysis contact mechanism of head/ disk interface on hard disk drive, many techniques of analysis have been developed. Acoustic Emission sensor can be used for detect elastic energy of contact at head/disk interface. This work presents a good understanding of slider characteristics in frequency domain. The results show that torsional and bending mode of slider are dominant in head/disk contact.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.273-274
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• 2002

In order to evaluate the flying characteristics of slider, the acoustic emission (AE) as well as friction signals are typically utilized. In this work the frequency spectrum analysis is performed using the AE signal obtained during the head/disk interaction such as load/unload mechanism using ramp, impact situation in the presence of a bump on disk surface and other contact phenomena including particle interaction. It was shown that the influence of impact can be characterized effectively in the AE frequency spectrum. As a result of this work, frequency spectrum analysis will be utilized with better understanding for studying the head/disk interface (HDI) characteristics and monitoring the particle interaction in HDI effectively.

• 한국산학기술학회논문지
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• 제12권7호
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• pp.2975-2981
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• 2011

본 논문에서는 얼굴 영상 처리와 음성 신호처리를 적용하여 오미자차가 인체 장기에 효과가 있는 차인지 그리고 있다면 어느 장기에 효용이 있는지에 대한 분석 방법을 제안하고자 한다. 이를 위해 우선 영상처리를 통해 오미자차를 섭취하기 전과 후의 얼굴 영상에서 우측 뺨 영역의 색상 변화를 비교 분석하였다. 아울러 오미자차 효능에 대해 보다 많은 사실 확보를 위해 성대 진동 및 음성 에너지의 크기를 분석하는 음성분석 실험을 수행하였다. 실험 결과 오미자차 섭취에 의해 폐의 기능이 원활해지면서 성대 진동 및 에너지 크기가 안정적으로 변했으며 오른쪽 뺨 부위의 b값이 증가하는 현상이 나타났다.

• 대한의생명과학회지
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• 제22권4호
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• pp.115-126
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• 2016

Audiometric calibration is a prerequisite for securing the reliability of audiometric test results by checking the internal consistency of the relevant instrument. The purpose of this review is to help instrument operators understand the calibration procedure of aural acoustic immittance instrument which is frequently used for objective assessment. By referring to the latest international standards and the national standards relevant to the aural acoustic immittance instrument, the following parameters will be reviewed: 1) introduction of performance characteristics, 2) detailed procedure of the calibration method. According to the newest international and national standards [IEC 60645-5 (2004), ANSI S3.39-1987 (R2012)], the aural acoustic immittance instrument basically includes six components: 1) calibration cavity, 2) acoustic immittance analysis system, 3) probe assembly/unit and signal, 4) pneumatic air-pressure pump system, 5) acoustic reflex activator system and 6) tympanogram and acoustic reflex plotting system, each of these components should meet set standards. The result of behavioral hearing tests is influenced by various complex factors including the examinee's cooperation, background noise of the examination room, measurement method, skill level of the audiologist and calibration status, but the objective hearing tests is more influenced by the calibration status of the instrument than any other factors. The audiologist should take full responsibility for the reliability of the hearing test result, so he/she should carry out the calibration check and adjustments of aural acoustic immittance instrument periodically and maintain the instrument continuously by referring to the newest standards and the manufacturer's instruction manual.

• 한국해양공학회지
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• 제34권4호
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• pp.277-284
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• 2020

Underwater acoustics, which is the study of phenomena related to sound waves in water, has been applied mainly in research on the use of sound navigation and range (SONAR) systems for communication, target detection, investigation of marine resources and environments, and noise measurement and analysis. The main objective of underwater acoustic remote sensing is to obtain information on a target object indirectly by using acoustic data. Presently, various types of machine learning techniques are being widely used to extract information from acoustic data. The machine learning techniques typically used in underwater acoustics and their applications in passive SONAR systems were reviewed in the first two parts of this work (Yang et al., 2020a; Yang et al., 2020b). As a follow-up, this paper reviews machine learning applications in SONAR signal processing with a focus on active target detection and classification.

• 한국공작기계학회논문집
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• 제17권1호
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• pp.50-58
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• 2008

The SM45C metallic coupons have been tested under static tensile loading with acoustic emission (AE) as the load-deflection curve mainly. In this study, we used AE to detect the yielding of material and AE techniques was applied to rapidly estimate the mechanical characteristics of a material. First, coupons without an artificial defect were tested at different cross-head speed. For all cases in this analysis, yielding point of SM45C coupons did not appear definitely compared to mild steel, whereas coupons start to generate AE counts upon yielding. So all cases are normalized to know the possibility of accelerated life test of a material. And next, coupons with different from sizes of circular hole defects were tested at the same cross-head speed of 5 mm/min. Results were classified into 3 classes and analyzed by AE amplitude & signal strength as a function of time. Summarizing the specific conclusions, we need to additional research considering plate with width-ratio in order to estimate the fracture mechanism.

• 말소리와 음성과학
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• 제10권2호
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• pp.7-14
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• 2018

The paper investigates the acoustic characteristics of English fricatives in the TIMIT corpus, with a special focus on the role of voicing in rendering fricatives in American English. The TIMIT database includes 630 talkers and 2,342 different sentences, and comprises more than five hours of speech. Acoustic analyses are conducted in the domain of spectral and temporal properties by treating gender, voicing, and place of articulation as independent factors. The results of the acoustic analyses revealed that acoustic signals interact in a complex way to signal the gender, place, and voicing of fricatives. Classification experiments using a multiclass support vector machine (SVM) revealed that 78.7% of fricatives are correctly classified. The majority of errors stem from the misclassification of /θ/ as [f] and /ʒ/ as [z]. The average accuracy of gender classification is 78.7%. Most errors result from the classification of female speakers as male speakers. The paper contributes to the understanding of the effects of voicing and gender on fricatives in a large-scale speech corpus.