• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 제7회 압연 심포지엄
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• pp.97-102
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• 2009

In hot strip rolling, sound prediction of the temperature of the strip is vital for achieving the desired finishing mill draft temperature (FDT). In this paper, a precision on-line model for the prediction of temperature distributions along the thickness of the strip in the finishing mill is presented. The model consists of an analytic model for the prediction of temperature distributions in the inter-stand zone, and a semi-analytic model for the prediction of temperature distributions in the bite zone in which thermal boundary conditions as well as heat generation due to deformation are predicted by finite element-based, approximate models. The prediction accuracy of the proposed model is examined through comparison with predictions from a finite element process model.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.45-51
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• 2002

An acoustic finite element model of a bridge is developed to evaluate the noise generated by the traffic-induced vibration of the bridge. The dynamic response of a multi-girder bridge, modeled by a 3-dimensional frame element model, is analyzed with a 3-axle 8 DOFs truck model and a 5-axle 13 DOFs semi-trailer. The flat plate element is used to analyze the acoustic pressure due to the fluid-structure interactions between the vibrating surface and contiguous acoustic fluid medium. The radiation fields of noise with a specified distribution of vibrating velocity and pressure on the structural surface are also computed using the Kirchhoff-Helmholtz integral. Although the noise produced by the bridge vibration is not serious in itself, which is below the audible frequency range, it should be considered as an interaction problem between vehicle noise and bridge vibration noise in order to evaluate the traffic noise around the bridge.

• Journal of Mechanical Science and Technology
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• 제19권8호
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• pp.1611-1620
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• 2005

This paper shows the use of wavelet transformation combined with inverse acoustics to reconstruct the surface velocity of a noise source. This approach uses the boundary element analysis based on the measured sound pressure at a set of field points, the Helmholtz integral equations and wavelet transformation for reconstructing the normal surface velocity field. The reconstructed field can be diverged due to the small measurement errors in the case of nearfield acoustic holography (NAH) using an inverse boundary element method. In order to avoid this instability in the inverse problem, the reconstruction process should include some form of regularization for enhancing the resolution of source images. The usual method of regularization has been the truncation of wave vectors associated with small singular values, although the order of an optimal truncation is difficult to determine. In this paper, a wavelet transformation is applied to reduce the computation time for inverse acoustics and to enhance the reconstructed vibration field. The computational speed-up is achieved, with solution time being reduced to $14.5\%$.

• Advances in nano research
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• 제9권4호
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• pp.263-276
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• 2020

In this article, the acoustic responses of free vibrated natural fibre-reinforced polymer nanocomposite structure have been investigated first time with the help of commercial package (ANSYS) using the multiphysical modelling approach. The sound relevant data of the polymeric structure is obtained by varying weight fractions of the natural nanofibre within the composite. Firstly, the structural frequencies are obtained through a simulation model prepared in ANSYS and solved through the static structural analysis module. Further, the corresponding sound data within a certain range of frequencies are evaluated by modelling the medium through the boundary element steps with adequate coupling between structure and fluid via LMS Virtual Lab. The simulation model validity has been established by comparing the frequency and sound responses with published results. In addition, sets of experimentation are carried out for the eigenvalue and the sound pressure level for different weight fractions of natural fibre and compared with own simulation data. The experimental frequencies are obtained using own impact type vibration analyzer and recorded through LABVIEW support software. Similarly, the noise data due to the harmonically excited vibrating plate are recorded through the available Array microphone (40 PH and serial no: 190569). The numerical results and subsequent experimental comparison are indicating the comprehensiveness of the presently derived simulation model. Finally, the effects of structural design parameters (thickness ratio, aspect ratio and boundary conditions) on the acoustic behaviour of the natural-fibre reinforced nanocomposite are computed using the present multiphysical model and highlighted the inferences.

• 한국철도학회논문집
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• 제19권1호
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• pp.1-10
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• 2016

본 논문은 고속열차 객실 내 유리창의 차음 성능을 향상시키기 위한 기반연구로, 접합유리에 사용되는 고분자 필름의 물성과 음향학적 특성을 분석하여 그 상관관계를 살펴보고자 하였다. 기존에 사용되고 있는 PVB(polyvinyl butyal) 필름 및 다른 단량체 비율을 가지는 PVB 유도체, 그리고 유리 사이 차음재로 사용가능 한 PC(polycarbonate)의 동적기계적 특성을 분석(DMA)하였다. DMA 분석을 통해 상온에 가까운 온도범위에서 유리전이온도($T_g$)를 가지며 tan ${\delta}$(loss tangent) 값이 큰 것으로 나타난 PVB-HEMU 시편의 댐핑(damping) 성능이 가장 우수할 것으로 예측하고, 이를 고속철도 차량의 접합유리창과 동일한 구조에서의 투과손실 시험과 해석을 통해 검증하고자 하였다. 접합필름의 종류에 따른 유리창 투과손실 값을 투과손실 측정(인텐시티법)과 FE 해석을 이용해 도출하고, 고분자 필름의 물성과 음향성능 간 상관관계 분석을 위한 기초자료를 구축하였다.

• 한국도서관정보학회지
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• 제10권
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• pp.229-265
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• 1983

Many changes have been made on the cataloging rules on filmstrips and slides all the way from the Cox's rules of 1963 to AACR 2 of 1978. The purpose of this study is to analyze eight major British and American cataloging rules on filmstrips and slides, from the results of which to identify what major changes have been made chronologically, and to clarify major differences among them in describing the form ol Physical Description Area. The findings of the study can be summarized as follows: 1. In order to make a clear distinction from one element to the other in Physical Description Area, the use of punctuation has been made more concrete. In AACR 2, various punctuations in accordance with the each element's character are used. 2. The rules on the describing the number of physical units of filmstrips have got more and more specified. 3. The descriptive form of specific material designation is closely related to the existence or nonexistence of rules on the general material designation in the body of entry. Therefore, the rules of AECT and CLA having rules on the general material designation do not use the specific material designation in Physical Description Area. On the other hand, ISBD(NBM), LA rules and AACR 2 which makes it optional to use the general material designation prescribe to use the specific material designation. 4. As for the descriptions of the physical status other than the unit and size of the filmstrips and slides, the first LC card and Cox's rules, had the color designation, and the CLA rules had sound designation. In the LA rules, AACR1(Chapter 12 Revised) and AACR 2, the detailed description of the physical status including the indication of color, sound, kind of frame, time etc. has become more and more important for Physical Description Area. 5. All the rules adopt millimetre as the measuring unit of the size of filmstrips. For the slides, most rules employ inch instead. But LA rules and ISBD(NBM) use centimeters, and AACR 2 takes either inch or centimeters. 6. Most rules, including Cox's rules, give the information on the accompanying materials. The information has been added as the last element of the Physical Description Area in the AACR 2, and recognized very important.

• International Journal of Safety
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• 제6권2호
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• pp.1-7
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• 2007

In this study mechanical strength of A53B carbon steel was analyzed using several types of test specimens directly machined from oil recycling pipe experienced a failure due to hydrogen attack in chemical plants. High temperature hydrogen attack (HTHA) is the damage process of grain boundary facets due to a chemical reaction of carbides with hydrogen, thus forming cavities with high pressure methane gas. Driven by the methane gas pressure, the cavities grow on grain boundaries forming intergranular micro cracks. Microscopic optical examination, tensile test, Charpy impact test, hardness measurement, and small punch (SP) test were performed. Carbon content of the hydrogen attacked specimens was dramatically reduced compared with that of standard specification of A53B. Traces of decarburization and micro-cracks were observed by optical and scanning electron microscopy. Charpy impact energy in hydrogen attacked part of the pipe exhibited very low values due to the decarburization and micro fissure formation by HTHA, on the other hand, data tested from the sound part of the pipe showed high and scattered impact energy. Maximum reaction forces and ductility in SP test were decreased at hydrogen attacked part of the pipe compared with sound part of the pipe. Finite element analyses for SP test were performed to estimate tensile properties for untested part of the pipe in tensile test. And fracture toughness was calculated using an equivalent strain concept with SP test and finite element analysis results.

• 대한기계학회논문집A
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• 제34권8호
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• pp.1035-1044
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• 2010

머리관련 전달함수는 음원으로부터 이도의 입구까지 소리의 전달함수로 인간이 소리의 위치를 판단하는 데 중요한 역할을 하는 함수이다. HRTF 는 개인간의 편차가 크게 나는 것으로 알려져 있다. 본 논문에서는 한국인의 평균두형에 관해서 HRTF 를 해석하는 경계요소해석 모델을 개발하고 해석 결과와 실험결과와의 비교를 통해서 모델을 검증하였다. 또한 특정 성인에 대하여 CT 촬영을 통하여 두형, 귓바퀴 및 이도의 형상을 획득하여 이를 바탕으로 이도 내의 음향응답을 전 가청주파수에서 해석할 수 있는 모델을 개발하고 실험과의 비교를 통하여 모델을 검증하였다. 개발된 모델을 이용, 경계요소 해석을 수행하고 한국인 HRTF 의 특성에 영향을 미치는 인자를 살펴보았다.

• 한국철도학회논문집
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• 제19권2호
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• pp.124-134
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• 2016

철도 선로에 근접하여 설치하는 근접 저상 방음벽은 방음벽 높이를 저감시키기 위한 방안으로 외국에서는 많은 연구가 수행되고 있으나 국내에서의 연구는 매우 미흡한 실정이다. 본 논문에서는 근접 저상 방음벽의 음향특성을 파악하고자 축척 모형을 제작하여 성능평가를 수행하였다. 실험결과, 'ㄱ'자형 방음벽 설치 시에는 방음벽의 안쪽뿐만 아니라 상부에도 흡음재를 설치하는 것이 삽입손실의 개선효과가 있는 것으로 분석되었고, 방음벽의 삽입손실 평가를 위해 단순한 경험식 대신에 경계요소법과 같은 보다 해석적인 방법으로 삽입손실을 예측할 필요가 있다. 또한, 흡음재를 부착한 근접 방음벽을 설치하면 승객 위치에서의 소음 증가현상은 미미한 것으로 분석되었다. 그리고, 근접 방음벽의 음향성능 예측을 위해 2차원 경계요소법을 이용한 소음해석을 수행하였으며, 측정결과와의 비교 분석을 수행함으로서 예측 프로그램의 활용 가능성을 검증하였다.

• 한국음향학회지
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• 제6권3호
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• pp.17-22
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• 1987

새로운 차음성능 측정방법인 표면인텐시티법을 이용하여 실제 건축물의 현장에서 각부위별 차음성능 평가하고. 이를 종래의 음압측정방법과 은향인텐시티법 및 이론계산에 의한 결과 치 와 비교 . 검토하였다. 표면인텐시티법에 의한 건물부위의 차음성능 측정결과치는 음향인 텐시티법 및 이론계산에 의한 결과치와 잘 일치하였으며, 표면 인텐시티법은 음향인텐시티 법과 더불어 종래의 음압측정방법에 비해 측정시 주위 암소음 및 flanking transmission의 영향을 적게 받는 것으로 나타났다.