• ETRI Journal
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• 제37권3호
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• pp.471-479
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• 2015

Traditional designs of cognitive radio (CR) focus on maximizing system throughput. In this paper, we study the joint overlay and underlay power allocation problem for orthogonal frequency-division multiple access-based CR. Instead of maximizing system throughput, we aim to maximize system energy efficiency (EE), measured by a "bit per Joule" metric, while maintaining the minimal rate requirement of a given CR system, under the total power constraint of a secondary user and interference constraints of primary users. The formulated energy-efficient power allocation (EEPA) problem is nonconvex; to make it solvable, we first transform the original problem into a convex optimization problem via fractional programming, and then the Lagrange dual decomposition method is used to solve the equivalent convex optimization problem. Finally, an optimal EEPA allocation scheme is proposed. Numerical results show that the proposed method can achieve better EE performance.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 추계학술대회 논문집
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• pp.733-739
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• 2000

This paper is described the development of on-line partial discharge detector for high voltage apparatus. This detector consists of acoustic and high frequency current sensors, amplifier part, A/D converter part, data communication part and computer. The contents of paper are characteristics of units and digital signal processing for reducing noise in partial discharge detection. We seek methods to do good digital signal processing for detection of partial discharge. We apply digital filtering methods to the elect Tic signal and a cross con-elation to the acoustic signal. This paper shows the characteristics of these filtering method and cross con-elation in partial discharge detection.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.582-587
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• 2011

Acoustic Emission(AE) is widely used for early detection of faults for rotating machinery in these days because of its high sensitivity. AE signal has to need for transferring to low frequency range for the spectrum analysis included the fault mechanism. In transferring process, we lose a lot of fault information caused by unusable signal processing method. Discrete Wavelet Transform(DWT) is a method of signal processing for AE signatures, but the pattern of its mother function is not optimized with AE signals. So, we can lose the fault information when we want to use the DWT for AE signal. Therefore, in this paper, we will propose a novel pattern for DWT mother function, which is optimized with AE signals. And it will be applied to compare the results of DWT by daubechie and novel pattern.

• 동력기계공학회지
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• 제15권1호
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• pp.18-23
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• 2011

Image processing has provided powerful techniques to extract from the acoustic signals the desired information on evaluation for leakage existence, leakage rate, and searching for leakage location, etc. The imagery NDE data available can add additional and significant dimension in nondestructive evaluation(NDE) information and thus for exploiting in applications. To extract such information the use of advanced image processing techniques is much needed. In recent years, there has been much increased use of acoustic signal image processing techniques in acoustic NDE. This approach will increase the efficiency of inspection procedures and reduce inspection time. In this paper we are concerned only with This paper is concerned mainly with the use of advanced image processing techniques in valve leakage detection and advanced image restoration and enhancement methods, which attempt to evaluate promptly by a visualization method the acoustic sources while detecting the valve leakage.

• Journal of Biosystems Engineering
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• 제24권3호
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• pp.253-258
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• 1999

This study was conducted to develop an automatic egg inspection system for detecting creaked eggs based on acoustic impulse response. This system includes a sound generator, a sound sensor with signal conditioner, and a computer. The sound generator that hit the sharp of the dull edges of an egg was constructed with a ceramic ball pendulum attached to a rotary type solenoid. The signal conditioner included a pre-amplifier and a digital signal processing (DSP) board. The parameters for distinguishing cracked and normal eggs were the area, the geometric centroid and the resonance frequency of power spectrum of the acoustic signal generated. An algorithm for on-line detection of the continuous transferring eggs was developed. The performance tests resulted with 91% success rate to separate cracked and normal eggs at the rate of 1 second per an egg.

• 한국정밀공학회지
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• 제11권4호
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• pp.69-76
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• 1994

AE(Acoustic Emission) signal is correlated to workpiece material, cutting conditions and tool geometry during metal cutting. The relationship between AE signal and cutting parameters can be obtained by theoretical model and experiments. The value of CR(Count Rate) is nearly constant in stable cutting, but when the chatter vibration occours, the value of CR is rapidly increased due to the vibration deformation zone. By experimental signal processing of AE, it is more effective than by RMS(Root Mean Square) measurement to detect the threshold of chatter vibration by CR measurement.

• 한국음향학회지
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• 제36권1호
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• pp.57-63
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• 2017

본 논문에서는 FxLMS(Filtered-x Least Mean Square) 알고리즘을 이용한 단일 센서 기반의 능동 반향음 제어 알고리즘을 제안한다. 제안 알고리즘은 먼저 단일 센서 입력 신호로부터 입사음과 반향음을 분리하고, 분리된 신호들을 사용하여 반향음과 반대 위상을 갖는 제어 신호를 생성한다. 제어 신호는 센서 위치에서 반향음과 중첩되어 반향음의 음압을 감소시킨다. 적절한 신호 분리를 위해 반향 음향 경로와 제어 음향 경로가 필요하며 이는 swept sine 신호를 이용해 측정한 음향 응답으로부터 사전에 구할 수 있다. 효용성을 검증하기 위해 DSP(Digital Signal Processing) 보드를 사용하여 제안된 알고리즘을 실시간으로 구현하였으며, 공기 중 음향 덕트 환경에서 1 kHz 버스트 신호에 대해 반향음이 11.6 dB 감소함을 확인 하였다.

• 한국해양공학회지
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• 제34권3호
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• pp.227-236
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• 2020

Underwater acoustics, which is the domain that addresses phenomena related to the generation, propagation, and reception of sound waves in water, has been applied mainly in the research on the use of sound navigation and ranging (SONAR) systems for underwater communication, target detection, investigation of marine resources and environment mapping, and measurement and analysis of sound sources in water. The main objective of remote sensing based on underwater acoustics is to indirectly acquire information on underwater targets of interest using acoustic data. Meanwhile, highly advanced data-driven machine-learning techniques are being used in various ways in the processes of acquiring information from acoustic data. The related theoretical background is introduced in the first part of this paper (Yang et al., 2020). This paper reviews machine-learning applications in passive SONAR signal-processing tasks including target detection/identification and localization.

• Smart Structures and Systems
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• 제23권2호
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• pp.173-184
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• 2019

The main objective of this study is to evaluate the true fracture energy and monitor the damage progression in steel fibre reinforced concrete (SFRC) specimens using acoustic emission (AE) features. Four point bending test is carried out using pre-notched plain and fibre reinforced (0.5% and 1% volume fraction) - concrete under monotonic loading. AE sensors are affixed at different locations of the specimens and AE parameters such as rise time, AE energy, hits, counts, amplitude and duration etc. are obtained. Using the captured and processed AE event data, fracture process zone is identified and the true fracture energy is evaluated. The AE data is also employed for tracing the damage progression in plain and fibre reinforced concrete, using both parametric- and signal- based techniques. Hilbert - Huang transform (HHT) is used in signal based processing for evaluating instantaneous frequency of the acoustic events. It is found that the appropriately processed and carefully analyzed acoustic data is capable of providing vital information on progression of damage on different types of concrete.

• The Journal of the Acoustical Society of Korea
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• 제27권3E호
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• pp.104-111
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• 2008

Recently, a method for robust time reversal focusing has been introduced to extend the period of stable focusing in time-dependent ocean environments [S. Kim et al., J. Acoust. Soc. Am. 114, 145-157, (2003)]. In this study, concept of focal-size broadening based on waveguide invariant theory in an ocean time reversal acoustics is described. It is achieved by imposing the multiple location constraints. The signal vector used in multiple location constraints are found from the theory on waveguide invariant for frequency band corresponding the extended focal range. The broadening of foci in an ocean waveguide can play an important role in the application of time reversal processing, particularly to the underwater acoustic communication with moving vehicles. The proposed method is demonstrated in the context of the underwater acoustic communication from the transmit/receive array (TRA) to a slowly moving vehicle.