• 한국소음진동공학회논문집
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• 제25권2호
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• pp.75-82
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• 2015

Noises from the large scale marine propeller are calculated numerically on non-cavitation condition. The hydrodynamic analysis is carried out by potential based panel method with time marching free wake approach. The distribution of hydrodynamic loads on the propeller surface and noise signals are obtained using the unsteady Bernoulli's equation and the Farasssat's formula respectively. It turns out that the noise signal at the narrow band shows strong peak at the blade passage frequency, and the peak value at the 1/3 octave band also shows the same trend. Noise signals and directivity patterns for both the thickness and the loading noise are compared with each other. The directivity pattern for the loading noise shows minor lobe at the backward side of the rotating disc plane.

• 한국광학회지
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• 제18권1호
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• pp.14-18
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• 2007

실리카 코어 주변에 주기적인 공기층을 가지는 광자결정 광섬유는 넓은 파장 영역을 통한 단일모드의 구현 또는 1옥타브 이상의 광대역 연속광 발생과 같은 기존의 광섬유로는 불가능한 독특한 특성을 갖도록 유연하게 설계할 수 있다. 광자결정 광섬유의 설계에 사용되는 변수로는 공기층의 직경과 간격이 있으며 이러한 변수의 조절을 위한 공정을 도입하여 넓은 파장영역을 통한 단일모드 구현과 높은 비선형 특성을 가지는 광자결정 광섬유를 각각 제작 하였고 수치적 계산과 실험을 통해 그 특성을 살펴보았다.

• ETRI Journal
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• 제38권6호
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• pp.1218-1228
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• 2016

This paper proposes a robot hand for a violin-playing robot and introduces a newly developed robot finger. The proposed robot hand acts as the left hand of the violin-playing robot system. The violin fingering plays an important role in determining the tone or sound when the violin is being played. Among the diverse types of violin fingering playing, it is not possible to produce vibrato with simple position control. Therefore, we newly designed a three-axis load cell for force control, which is mounted at the end of the robot finger. Noise is calculated through an analysis of the resistance difference across the strain gauge attached to the proposed three-axis load cell. In order to ensure the stability of the three-axis load cell by analyzing the stress distribution, the strain generated in the load cell is also verified through a finite element analysis. A sound rating quality system previously developed by the authors is used to compare and analyze the sound quality of the fourth-octave C-note played by a human violinist and the proposed robot finger.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2002년도 하계학술발표대회 논문집 제21권 1호
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• pp.53-56
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• 2002

본 논문은 2채널 스피커를 사용하여 청취자에게 보다 입체적인 음향 효과를 제시하기 위하여 크로스토크현상을 제거하고 청취자의 보다 자유로운 청취를 위해 최적 청취영역 확대를 위한 실험과 시스템 구현에 관한 것이다. 정면에 위치한 두 스피커로부터 교차경로인 크로스토크를 제거하기 위해 음질의 왜곡을 최소화하는 자유음장 모델을 이용하여 구현한 트랜스오럴 필터 사용하였고 최적 청취영역의 확대를 위해 스피커는 BPF(Band Pass Filter)를 이용하여 저주파와 고주파를 분리하여 각각 재생할 수 있는 스피커를 구성하였으며 저주파 영역은 제외하고 중고주파 영역을 이용하였으며 기존 크로스토크제거 시스템을 사용하여 고정된 한 점의 청취영역에서 좌${\cdot}$우로 5Cm씩 이동하au 100Cm까지 측정한 결과 30Cm, 55Cm, 75Cm, 90Cm, 100Cm에서 크로스토크제거됨을 알 수 있는 음의 분리도가 5dB이상 나타났다. 실험 결과 얻어진 각 지점들로부터 자유음장 모델을 이용하여 트랜스오럴 필터링 하였으며 각각의 간섭현상을 막기 위해 주파수 영역에서 심리음향에 기초한 1/3-Octave Band Pass Filter를 사용하여 음질 보상을 실시하였다. 음원을 제작하여 기존의 2채널 시스템에서 제시하는 음원을 각각의 위치의 음원과 비교하여 음질 평가를 실시하였으며 기존의 트랜스오럴 필터와 비교평가를 실시하였다.

• 항공우주기술
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• 제1권2호
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• pp.91-104
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• 2002

우주 발사체 및 과학관측로켓에 유발되는 음향 하중의 주 원인은 추진기관의 제트 소음에 의한 것이다. 따라서 성공적인 임무 수행을 위한 음향 하중의 저감을 위해서는 반드시 추진 기관의 제트 소음(초음속)의 특성을 파악하는 것이 필요하다. 이를 위해 먼저 제트 유동에 의한 음향 하중의 발생 메카니즘을 살펴보았다. 그리고, 음향 하중에 영향을 주는 인자를 도출하고, 도출된 인자에 따른 음향 하중의 특성 변화를 살펴보았다. 3단형 과학 관측 로켓(KSR-III)의 음향 하중의 시공간적인 특성을 엔진 연소 시험시 측정된 소음 신호를 이용하여 분석하였다. KSR-III의 음향 하중의 최대값은 250 Hz, 500 Hz의 옥타브 밴드에 집중되어 있으며, 공간적으로 랜덤함을 알 수 있었다. 또한 추후 음향 하중의 특성 파악을 위한 자체적인 연구 방향을 제안하였다.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.1015-1035
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• 2015

A three-dimensional (3D) numerical analysis for the train-bridge interaction (TBI) system is actively developed in this study in order to investigate the vibration characteristics of rigid-frame reinforced concrete (RC) viaducts in both vertical and lateral directions respectively induced by running high-speed trains. An analytical model of the TBI system is established, in which the high-speed train is described by multi-DOFs vibration system and the rigid-frame RC viaduct is modeled with 3D beam elements. The simulated track irregularities are taken as system excitations. The numerical analytical algorithm is established based on the coupled vibration equations of the TBI system and verified through the detailed comparative study between the computation and testing. The vibration responses of the viaducts such as accelerations, displacements, reaction forces of pier bottoms as well as their amplitudes with train speeds are calculated in detail for both vertical and lateral directions, respectively. The frequency characteristics are further clarified through Fourier spectral analysis and 1/3 octave band spectral analysis. This study is intended to provide not only a simulation approach and evaluation tool for the train-induced vibrations upon the rigid-frame RC viaducts, but also instructive information on the vibration mitigation of the high-speed railway.

• 해양환경안전학회지
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• 제16권1호
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• pp.135-140
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• 2010

선박에서의 주요한 진동발생 원인으로는 주기관과 프로펠러에 의한 것이다. 이러한 가진원으로부터 발생한 진동은 선박에 탑재된 장비의 내구성에 악영향을 미치고, 선박의 승조원에게도 불쾌감 등의 나쁜 영향을 미치게 된다. 본 연구에서는 선박에서 발생하는 진동을 계측하지 위한 시스템을 구축하였고 실제 실습선의 거주공간에서 발생하는 진동을 계측하였으며, 계측된 진동을 바탕으로 ISO6954:2000E에 의거하여 거주성 평가를 행하였다.

• 한국소음진동공학회논문집
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• 제18권11호
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• pp.1199-1205
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• 2008

The vehicle design engineers have studied the method of applying damping materials to the vehicle bodies by computer simulations and experimental methods in order to improve the vibration and noise characteristics of the vehicles. The unconstrained layer damping, being concerned with this study, has two layers(base layer and damping layer) and proyides vibration control of the base layer through extensional damping. Generally this kind of surface damping method is effectively used in reducing structural vibration at frequencies beyond 150Hz. The most important thing is how to apply damping treatment with respect to location and size of the damping material. To solve these problems, the current experimental methods have technical limits which are cumbersome, time consuming, and expensive. This Paper proposes a method based on finite element method and it employes averaged ESE(element strain energy) percent of total of dash panel assembly for 1/1 octave band frequency range by MSC/NASTRAN. The regions of high ESE percent of total are selected as proposed location of damping treatment. The effect of damping treatment is analyzed by comparing the frequency response function of the SPCC bare Panel and the damping treated panels.

• Structural Engineering and Mechanics
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• 제71권2호
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• pp.131-138
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• 2019

It is necessary to predict subway induced vibration if a new subway is to be built. To obtain the vibration response reliably, a three-dimensional (3D) FEM model, consisting of the tunnel, the soil, the subway load and the building above, is established in MIDAS GTS NX. For this study, it is a six-story frame structure built above line 3 of Guangzhou metro. The entire modeling process is described in detail, including the simplification of the carriage load and the determination of model parameters. Vibration measurements have been performed on the site of the building and the model is verified with the collected data. The predicted and measured vibration response are used together to assess vibration level due to the subway traffic in the building. The No.1 building can meet work and residence comfort requirement. This study demonstrates the applicability of the numerical train-tunnel-soil-structure model for the serviceability assessment of subway induced vibration and aims to provide practical references for engineering applications.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1998년도 Proceedings of International Workshop on Advanced Image Technology
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• pp.189-194
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• 1998

We introduce a new zerotree scheme that effectively exploits the inter-scale self-similarities found in the octave decomposition by a wavelet transform. A zerotree is useful to efficiently code wavelet coefficients and its efficiency was proved by Shapiro's EZW. In the coding scheme, wavelet coefficients are symbolized and entropy-coded for more compression. The entropy per symbol is determined from the produced symbols and the final coded size is calculated by multiplying the entropy and the total number of symbols. In this paper, were analyze produced symbols from the EZW and discuss the entropy per symbol. Since the entropy depends on the produced symbols, we modify the procedure of symbolic streaming out for the purpose. First, we extend the relation between a parent and children used in the EZW to raise a probability that a significant parent has significant children. The proposed relation is flexibly extended according to the fact that a significant coefficient is highly addressed to have significant coefficients in its neighborhood. The extension way is reasonable because an image is decomposed by convolutions with a wavelet filter and thus neighboring coefficients are not independent with each other.