• 센서학회지
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• 제31권6호
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• pp.441-447
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• 2022

This study describes a novel method for detecting and measuring partial discharge (PD) on an electrical facility such as an insulated power cable or switchgear using fiber optic sensing technology, and a distributed acoustic sensing (DAS) system. This method has distinct advantages over traditional PD sensing techniques based on an electrical method, including immunity to electromagnetic interference (EMI), long range detection, simultaneous detection for multiple points, and exact location. In this study, we present a DAS system for PD detection with performance evaluation and experimental results in a simulated environment. The results show that the system can be applied to PD detection.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.182-186
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• 2000

The porous woven hose is recently considered as an effective element of automotive intake systems. In order to predict the acoustic performance of an intake system with a porous woven hose, the information on the acoustic wall impedance is required. In this article, a measurement technique that is valid over the low frequency range and without mean flow condition is presented. The measurement is performed in a cylindrical chamber with a concentric layout of the sample and the resistance is estimated from measured reactance and transmission loss data. It is observed that the measured transmission loss for a porous woven hose with an arbitrary length agrees well with the predicted one that uses the estimated impedance for a small sample length.

• 센서학회지
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• 제19권6호
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• pp.490-496
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• 2010

In this study, in order to overcome the weakness of acoustic field analysis which is generally used for ultrasonic probe performance evaluation, automatic acoustic field measurement system and evaluation parameters were proposed. The comparisons between acoustic field simulation and measured acoustic distribution data of normal and abnormal channels were conducted to evaluate the availability of proposed system and evaluation parameters. First, the impulse response characteristic of sample probe was investigated to classify the normal elements and abnormal elements. And then, normal channels and abnormal channels with abnormal element were chosen. The suggested 12 evaluation parameters were calculated using the acoustic fields of these channels. The availability of proposed automatic acoustic field measurement system and evaluation parameters was confirmed. And the performance evaluation of ultrasonic probe using acoustic field analysis could be easier and faster.

• 한국해양환경ㆍ에너지학회지
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• 제18권3호
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• pp.216-222
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• 2015

기존의 자동음파전달속도 측정시스템을 이용하여 해양퇴적물의 음향특성을 측정하는 경우 최초도달신호시간의 결정에 발생하는 오류와 측정 절차의 번거로움 등의 몇 가지 문제점들이 존재한다. 이러한 문제점을 개선하기 위하여 PXI모듈을 이용한 LabVIEW기반의 측정 시스템을 개발하였다. 새로운 측정시스템을 검증하기 위해 동일한 시료와 실험환경에서 기존 시스템과 병행하여 측정하였다. 그 결과 1~2%의 음파전달속도 측정오차를 보였으며 음파감쇠 역시 기존 시스템과 유사한 결과 값을 도출하였다. 새로이 개발된 PXI(PCI eXtentions for Instrumentation)를 이용한 LabVIEW 기반 음향특성 측정시스템은 퇴적물의 음향특성을 보다 신속하고 효율적으로 측정할 수 있고 측정 자료뿐만 아니라 분석된 신호의 원시자료에 대해서도 지속적인 데이터베이스를 구축할 수 있다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권12호
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• pp.649-654
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• 2003

The simplest method for measuring output currents of the three phase inverters is to measure them with three current sensors such as hall sensors. This method requires at least two current sensors, and these types of sensors are somewhat expensive. More economical method is measuring DC link current with a simple shunt resistor, then, reconstructing output current using the DC link current value and the switching status. However, in low speed region, the measurement becomes difficult and even impossible due to the requirement of minimum switching duration for A/D conversion. These problems can be overcome by limitation of switching duration. Limitation of switching, however, causes voltage and current distortion. Owing to compensation, distortion can be effectively suppressed. However these increase acoustic noise due to increment of current ripple. In this paper, a current measurement method is proposed, which can reduce minimum switching duration resulting in reduction of acoustic noise. The validity of proposed method is confirmed through experiment.

• Smart Structures and Systems
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• 제11권2호
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• pp.185-197
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• 2013

We developed a simultaneous strain measurement and damage detection technique using a pair of surface-mounted piezoelectric transducers and a fiber connecting them. This is a novel sensor configuration of the fiber acoustic wave (FAW) piezoelectric transducer. In this study, lead-zirconate-titanate (PZT) transducers are installed conventionally on a plate's surface, which is a technique used in many structural health monitoring studies. However, our PZTs are also connected with an optical fiber. A FAW and Lamb wave are simultaneously guided in the optical fiber and the structure, respectively. The dependency of the time-of-flight of the FAW on the applied strain is quantified for strain sensing. In our experimental results, the FAW exhibited excellent linear behavior and no hysteresis with respect to the change in strain. On the other hand, the well-known damage detection function of the surface-mounted PZT transducers was still available by monitoring the waveform change in the conventional Lamb wave ultrasonic path.

• 소음진동
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• 제9권1호
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• pp.141-148
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• 1999

Resilient mounting is effective measures to reduce the structure-borne noise and radiated noise for many applications. The acoustic stiffness (frequency-dependent stiffness) of resilient mounts is an important parameter required in order to model vibration isolation with high accuracy. It is general to use measurement method for obtaining acoustic stiffness of complex resilient mounts under static preload. In this paper, the principles of measuring acoustic stiffness were described and the developed test apparatus was introduced. Also, the feasibility of the test apparatus is illustrated by measurement results of a resilient mount.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.43-46
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• 1988

In this paper, a methodology for determination of the thickness of layer on a substrate using reflection acoustic microscope has been presented. It has been shown that the amplitude and the phase of reflection coefficient of the layer-substrate composite has been used for measurement of layer thickness, acoustic velosity, mass density of the layer material. The reflection acoustic microscope operating at a frequency of 15 MHz has been used for the experiment and the measured acoustic impedance value for aluminum sample has agreed with the published data, and the measured layer thickness for silver-glass composite has agreed with that measured using micrometer.

• 한국음향학회지
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• 제18권5호
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• pp.63-67
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• 1999

최근 들어 실내음향 특성의 측정과 평가를 위해 백색잡음을 이용한 잔향시간 측정법 대신에 임펄스응답을 이용한 측정법이 널리 이용되고 있다. 이 방법은 재현성이 우수하고 다양한 실내음향 특성치들을 한꺼번에 산출할 수 있어 전통적인 잔향시간 측정법에 비해 여러 가지 장점을 가지고 있다. 본 연구에서는 MLS(Maximum Length Sequence) 신호를 이용하여 실내에서의 임펄스 응답을 측정하고 이를 후처리(post-processing) 하여 잔향시간(EDT, RT), 명료도 지수(C50, C80, D, U50, U80, AI), 음의 크기 지수(G) 등, 주로 실의 음성음향 성능을 측정하는 시스템을 구축하였다. 본 연구에서는 측정시스템과 후처리 프로그램의 구성, 몇몇 실내공간에 대한 시험 측정의 결과 및 고찰 등에 대해 소개하고자 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.731-739
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• 2002

recently out door stadiums have been built as multi purpose stadium for athletic sports It hold but also various events and huge concerts. in the past, out-door stadium usually was built, but recently the out-door stadium which of the 50 ％ of roof covered by doom have been built increasingly. as the result, the sound obstacle is becoming very important. but a design of sound has become unplaned except some of the stadium, also rarely been built by sound-absorption material. as the result, the purpose of this study is investigating, analyzing the theory for plan of electric acoustic sound, a drawing of acoustic design and measurement a result value, comparison, evaluating a main sound factor with criteria of the Seoul City design. and reservation time, clearness, sound pressure level suitable for using purpose, so the necessary quantities will be added to financial budget of building acoustic design. and For verification, this contains acoustic analyser measurement and computer simulation and this study will find the solution of helping method.