• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.816-816
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• 2009

In order to attenuate structural waves in railway track, damped mass-spring absorber system and spring supported system are considered that are attached continuously along the beam length. A mathematical model is presented for the propagation of structural waves on a finitely long, periodically supported classical beam. The model in this paper could represent a railway track where the beam represents the rail and an appropriately chosen support type represents the pad/sleeper/ballast system of a railway track. And in this study, it is presented that the measurement method of health monitoring of railway track.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.852-855
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• 2008

In this paper, we proposed a new type's PZT actuator using surface acoustic wave. This actuator uses Rayleigh wave as an operational traveling wave. For the development of the actuator, each components of surface acoustic wave motor like PZT substrate, slider and IDT was studied theoretically and fabricated. For the measurement of transfer function of PZT substrate and operation of surface acoustic wave motor, network analyzer and 13.56MHz RF generator were used. Also the model which expresses the driving characteristic best was suggested and simulation was executed for the suggested model. And the future research works for improvement of SAW actuator was suggested.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.258-263
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• 2009

This paper describes an analysis of the stability and performance of a large-capacity flywheel energy storage system (FESS) supported by active magnetic bearings. We designed and manufactured the system that can store up to 5kWh of usable energy at the maximum speed of 18,000 rpm. In order to analyze the stability of the systems accurately, we derived a rigid body rotor model, flexible rotor model using finite-element method, and a reduced-order model using modal truncation. The rotor model is combined with those of active magnetic bearings, amplifiers, and position sensors, resulting in a system simulation model. This simulation model is validated against experimental measurements. The stability of the system is checked from the pole locations of the closed-loop transfer functions. We also investigated the sensitivity function to quantify the robustness of the systems to the disturbances such as mass imbalance and sensor noises.

• 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.

• Journal of Advanced Marine Engineering and Technology
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• 제22권1호
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• pp.77-84
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• 1998

Based on experimental analysis, the characteristics of pulsating pressure wave propagation is clarified by testing of 4-stroke gasoline engine. The pulsating pressure wave in exhaust system is generated by pulsating gas flow due to working of exhaust valve. The pulsating pressure wave is closely concerned to the loss of engine power according to back pressure and exhaust noise. It is difficult to exactly calculate pulsating pressure wave propagation in exhaust system because of nonlinear effect. Therefore, in the first step for solving these problems, this paper contains experimental model and analysis method which are applied two-port network analysis. Also, it shows coherence function, frequency response function, back pressure, and gradient of temperature in exhaust system.

• 한국전자파학회논문지
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• 제29권1호
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• pp.10-19
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• 2018

본 논문에서는 고주파 Radio-Frequency Interference (RFI) 측정용 프로브로 널리 쓰이는 Printed Spiral Coil(PSC)의 고주파 등가회로 모델이 제안되었다. 제안된 모델은 고주파 정합성을 확보하기 위하여 PSC의 설계변수에 기반한 분포 모델로 설계되었으며, 제안된 분포 등가회로 모델을 바탕으로 T-Pi 등가변환을 이용한 PSC의 고주파 해석적 모델 역시 새로이 제안되었다. 제안된 모델의 실제 고주파 RFI 측정 시 효용성을 확인하기 위하여, 임의의 RFI 노이즈 원으로 설계된 마이크로스트립 라인과 PSC 사이의 전달함수를 제안된 모델과 상호 인덕턴스를 결합하여 추출하였다. 제안된 PSC 모델의 자기 임피던스(self-impedance)와 전달함수는 3-dimensional field solver를 이용한 시뮬레이션 및 실 측정으로 검증되었으며, 6 GHz까지 높은 정합성을 보이는 것이 확인되었다. 제안된 PSC의 자기 임피던스 및 전달함수 모델은 GHz 영역의 고주파 통신대역에서의 RFI 측정용 프로브 설계 및 노이즈 간섭 예측에 활용될 수 있다.

• 소음진동
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• 제10권1호
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• pp.153-159
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• 2000

This paper presents a new method for including the dynamic stiffness of the stationary parts in rotordynamic analysis. As a consequence of the support dynamics, critical speeds are varied and/or additional critical speeds are introduced. Therefore, dynamic effects of the support are often significant in high speed turbomachinery, but most of analysis has considered the support as a rigid body or a simple structure. The proposed method is based on the coupled characteristics of the driving point and transfer frequency response functions of the support system to model the equivalent spring-mass series in finite element analysis. To demonstrate the applicability of the simulation procedures provided, it is applied to the rotor model of the double suction centrifugal pump. Results of the suggested equivalent-support rotor model including coupled effects agree well with the entire pump model.

• 오토저널
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• 제14권5호
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• pp.95-106
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• 1992

Active control of acoustic noise is an application area of adaptive digital signal processing with increasingly interest along the last year. This work studies the implementation of the multichannel LMS filter and the application of this algorithm for the reduction of the noise inside a vechicle cabin using a number of 'secondary sources' drived by adaptive filtering of a reference noise source. Firstly, we propose the use of an adaptive method for the time-varient optimal convergence factor. Secondly, we propose the use of adaptive delayed inverse model to estimate the elastic-acoustic transfer function presented in vechicle cabin. The original, primary source is often periodic, with a known fundamental frequency. A suitably filtered reference signal can thus be used to drive the secondary sources. An algorithm is presented for adapting the coefficients of an FIR filter feeding such a secondary source in such a way as to minimize the output of a suitably placed microphone. In this algorithm, the coefficients of adaptive filter driving an array of secondary sources can be adapted to minimize the sum of the squares of the outputs of a number of error microphones. The multichannel LMS algorithm displays that such an algorithm is considered suitable to used for the global suppression of noise in vehicle cabin.

• 한국통신학회논문지
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• 제19권8호
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• pp.1528-1535
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• 1994

본 논문에서는 적응 능동소음제어를 위한 새로운 오차경로 인식 방법을 통한 filtered-X LMS(least mean square) 알고리듬을 제안하였다. 제안한 알고리듬에서는 3개의 마이크로폰과 이중루프제어를 이용하여 오차경로의 전달 특성을 온라인으로 정확히 인식하도록 하였다. 덕트를 통한 소음이 정형파인 경우와 실제 공조기의 소음에 대하여 컴퓨터 시뮬레이션을 각각 수행한 결과, 제안한 방식은 입력소음에 비하여 각각 평균 29.1dB 및 10.4dB 정도의 소음레벨이 감쇠됨을 확인하였다. 이는 Eriksson의 방법보다 각각 평균 0.5dB 및 2.5dB 정도 개선된 것이다.

• 한국소음진동공학회논문집
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• 제18권6호
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• pp.642-653
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• 2008

이 연구는 중앙면 상에서 주성분 분석법을 이용하여 시간 및 주파수 영역에서 머리전달함수의 모형화 기법들을 다룬다. 시간영역의 머리전달함수, 복소수 값의 머리전달함수, 확장된 머리전달함수, 로그 크기의 머리전달함수에 기반하여 각각 주성분 분석법을 수행하여 얻은 네 가지 머리전달함수 모형들에 대해서 최소자승오차 관점에서 모형화 성능을 비교하고, 모형들간의 이론적인 관계를 살펴보는 것이 이 연구의 목적이다. 모형화에 사용되는 기저함수의 수가 동일하다면, 시간영역에서의 머리전달함수 혹은 확장된 머리전달함수에 기반한 모형이 복소수 값의 머리전달함수에 기반한 모형보다 최소자승오차 관점에서 더 효율적인 모형화 성능을 지닌다. 시간영역에서의 머리전달함수에 기반한 모형과 확장된 머리전달함수에 기반한 모형은 이론적으로 동일한 모형이며 서로 푸리에 변환 관계가 있다. 로그 크기의 머리전달함수에 기반한 모형은 다른 모형들과 모형화 성능 및 이론적인 관계를 비교할 수가 없는데, 이는 로그 크기의 머리전달함수에 기반한 모형은 머리전달함수의 크기 정보만을 로그 크기로 다루는 반면에 다른 모형들은 선형 크기로 머리전달함수의 크기와 위상정보를 모두 다루기 때문이다.