• 한국소음진동공학회논문집
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• 제24권6호
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• pp.437-443
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• 2014

Vibration testing is conducted for evaluate the fatigue resistance of responsible system over excitation situations and two kinds of vibration profiles, harmonic or random, are widely used in engineering fields. Harmonic excitation profile is adequate for the rotating machinery that is primarily exposed to the orderly excited force subjected for a rotating speed; Random profile is suitable for the non-stationary vibration input, that is a ground excitation for example. Recently, the sine on random(SOR) testing method was sometimes considered to represent the real excitation conditions since the measured response signals of a target system, expecially for moving mobility, shows usually a mixture of them. So, it is important to understand the accumulated fatigue damage over different excitation patterns, harmonic and/or random, to determine the efficient vibration profile of a target system. A uniaxial vibration testing with a notched simple beam was introduced to evaluate the fatigue damage for different excitation profiles and the best choice of vibration profile was concluded from those comparison of calculated fatigue damages.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.340-345
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• 2014

Vibration testing is conducted for evaluate the fatigue resistance of responsible system over excitation situations and two kinds of vibration profiles, harmonic or random, are widely used in engineering fields. Harmonic excitation profile is adequate for the rotating machinery that is primarily exposed to the orderly excited force subjected for a rotating speed; Random profile is suitable for the non-stationary vibration input, that is a ground excitation for example. Recently, the sine on random (SOR) testing method was sometimes considered to represent the real excitation conditions since the measured response signals of a target system, expecially for moving mobility, shows usually a mixture of them. So, it is important to understand the accumulated fatigue damage over different excitation patterns, harmonic and/or random, to determine the efficient vibration profile of a target system. A uniaxial vibration testing with a notched simple beam was introduced to evaluate the fatigue damage for different excitation profiles and the best choice of vibration profile was concluded from those comparison of calculated fatigue damages.

• 전기학회논문지
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• 제56권4호
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• pp.693-698
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• 2007

In general the distributed winding method is applied for induction motor in order to have the sinusoidal flux distribution. Recently the concentrated winding method is the interested technique so as to lower the material cost portion of copper coil. In the concentrated winding induction motor the harmonic flux and the torque deterioration by it would be occurred. To restrain ill effect of harmonic flux distribution by concentrated winding, the skew of rotor conduction bar is very important design variable. This study is focused on the optimal design of rotor bar's skew and winding turns for concentrated winding induction motor. In this study, the control method of harmonic parasitic torque in concentrated winding induction motor is proposed and validated its practicality through the experiment. As a result of this study, large skew angle which was not conventional in distributed winding was favorable in the concentrated winding induction motor. The concentrated winding induction motor which is designed per the proposed method of this study can be manufactured more cost effectively than conventional distributed winding.

• 한국소음진동공학회논문집
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• 제23권11호
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• pp.943-950
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• 2013

This paper discusses a harmonic response estimation method on the L$\acute{e}$vy plate with two opposite edges simply supported and the other two edges having free boundary conditions. Since the equation of motion of the plate is not self-adjoint, the modes are not orthogonal to each other on the domain. Noting that the L$\acute{e}$vy plate can be expressed using one term sinusoidal function that is orthogonal to other sinusoidal functions, this paper suggested the calculation method that is equivalent to finding a least square error minimization solution of the finite number of algebraic equations. Example problems subjected to a distributed area loading and a distributed line loading are defined and their solutions are provided. The solutions are compared to those of the commercial code, ANSYS. According to the verification results, it is expected that the suggested method will be useful to predict the forced response on the L$\acute{e}$vy plate with the distributed area or line loading conditions.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.710-711
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• 2014

In many cases, periodic noise occurs because most applications include motors, compressors and so on which have reciprocating motion. The noise usually contains tones at the fundamental frequency and at several higher harmonic frequencies in practice. For this type of noise, we developed a frequency-domain active noise control algorithm and determined that it's effective. However, the performance deteriorated for quasi-periodic noise. In this paper, we develop compensated frequency-domain active noise control algorithm for quasi-periodicity. And then, we implement computer simulation and compare the performance.

• 지구물리와물리탐사
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• 제2권4호
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• pp.180-183
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• 1999

도시화된 인구밀접지역과 인공잡음(예, 소음, 진동, 전력선 등)이 매우 심한 환경에서 양질의 탄성파 자료를 획득하기 위하여 기준점을 이용한 실험적 수준의 탄성파 측정시스템을 개발하였다. 소음과 전자파 잡음에 대한 상관측정(소음에 대한 상관측정의 센서는 마이크와 수진기 사용, 전자파에 대한 상관측정의 센서는 EM루프와 수진기 사용)을 각각 김포공항과 전라북도 김제시에서 수행하였으며, 또한 각 잡음의 측정 시계열에 대해 스펙트림 분석도 실시하였다. 소음에 의한 두 센서(마이크와 수진기)반응은 높은 상관성을 갖고 있으나, 두 센서 반응의 가장 큰 차이는 200Hz를 기준으로 저주파수 그리고 고주파수대역에서 일어나고 있다. 200Hz 이하의 주파수대역에서는 수진기를 통하여 측정한 잡음의 스펙트럴 에너지가 상대적으로 크고(예, 10Hz와 100Hz에서 각각 20dB 이상 큼) 200Hz 이상의 상대적인 고주파수에서는 마이크를 통하여 측정된 잡음의 수준이 높다(예, 500Hz에서 30dB 이상). 전체적으로 수진기를 통하여 측정된 잡음의 스팩트럴 파워는 주로 600Hz 이하에 집중되어 있는 반면에 마이크에 측정된 잡음의 파워는 주로 200Hz이상에서 분포하고 있다. 전력선 잡음을 가정하여 교류직류 인버터에서 발생한 전자파잡음에 대한 EM루프와 수진기를 통하여 측정한 전자파잡음은 각 센서에서 그 파형이 매우 일정하며, 또한 서로 간에 높은 상관성을 보였다. EM루프에 측정된 전자파잡음의 경우 60Hz에 대한 기수 조화주파수가 우수 조화주파수에 비하여 그 스펙트럴 에너지가 매우 크지만, 수진기의 경우는 그 차이가 거의 없었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.166-171
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• 2013

In this study, low noise designs of a Savonius wind turbines are numerically investigated. From a previous study, it was found that the high harmonic components whose fundamental frequency is higher than the BPF were found to be dominant in noise spectrum of a Savonius wind turbine. On a basis of this observation, S-shaped blade tip is proposed as a low design factors that decrease wind turbine noise by inducing phase differences in vortex shedding. The conventional Savonius and S-shaped turbines are investigated using Hybrid CAA method where flow field around the turbine are computed using CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow data. Noise reductions by these design factors are confirmed by comparing the predicted noise levels from these turbines.

• 한국통신학회논문지
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• 제28권3C호
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• pp.239-247
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• 2003

본 논문에서는 기존에 제안한 바 있는 EHC(Efficient Harmonic-CELP) 부호화기에 기반한 이중 전송률(2.4/4.0 kbps)의 개선된 하모닉-CELP(Improved Harmonic-CELP: IHC) 음성 부호화기를 제안한다. 제안된 IHC는 유/무성음 판별에 따라 유성음에서는 하모닉 추정, 하모닉 양자화, 하모닉 합성 및 잡음 혼합을 통한 자연성 제어 등의 과정을 통해, 무성음에서는 고속 CELP 방식을 통해 음성신호를 부호화/복호화한다. 또한 제안된 IHC는 EHC의 유/무성음 판별과 하모닉 추정 성능을 개선한다. 피치 이득과 에너지 등을 이용한 유/무성음 판별은 프레임 내의 에너지 변화 등에 의해 재판별된다. 하모닉 부호화에서는 첨점 추출과 델타 조정 방법을 이용하여 정확한 하모닉 추정을 하고, 혼합하는 잡음의 대역과 양을 적절하게 조절하여 자연성을 제어한다. 제안된 IHC 부호화기에 성능평가 결과, 비교 부호화기인 HVXC 연산량의 약 40%이내의 연산량으로 우수한 음질을 보임을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1991년도 춘계학술대회논문집; 한국해사기술연구소, 대전; 1 Jun. 1991
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• pp.7-9
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• 1991

차량 주행시 내부공간의 소음레벨의 변화를 "Booming"소음이라고 통칭하며, 이 소음의 주 원인은 엔진 회전수의 2차 하모닉(harmonic) 주파수 성분으로 구조적인 경로를 통하여 인체에 전달되게 된다. Booming 소음은 변화가 클 때 탑승자에게 큰 고통을 주며 차량 가치평가에 커다란 마이너스 요인이 된 다. 본 연구에서는 이러한 Booming 현상을 파악하고 대처하는 방법의 하나 로서 벡터해석법을 사용하고자 한다. 사용하고자 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.424-429
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• 2005

In this paper, the response characteristics of one to one resonance on the rectangular cantilever beam in which basic harmonic excitations are applied by nonlinear coupled differential integral equations are studied. This equations have 3-dimensional non-linearity of nonlinear inertia and nonlinear curvature. Galerkin and multi scale methods are used for theoretical approach to one to one internal resonance. Nonlinear response characteristics of 1st, 2nd, 3rd modes are measured from the experiment for basic harmonic excitation. From the experimental result, geometrical terms of nonlinearity display light spring effect and these terms play an important role in the response characteristics of low frequency modes. Dynamic behaviors in the out of plane are also studied.