• Title/Summary/Keyword: Tunnel Noise

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Cavitation and Noise Characteristics of High-Speed Propellers with Geometric Variations (고속 프로펠러의 형상변화에 따른 캐비테이션 및 소음 특성)

  • Jong-Woo Ahn;Young-Ha Park;Il-Sung Moon;Ki-Sup Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.38 no.3
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    • pp.23-30
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    • 2001
  • The cavitation noise of high-speed propellers was experimentally studied using new measurement device in KRISO cavitation tunnel. A series of cavitation noise tests were carried out for 6 propellers with various sections, loading distributions, and a different area ratio. From the experimental results, the noise characteristics for various cavitation patterns and the noise performance for a series of propellers were analyzed. These can be used for full-scale prediction study of the noise and optimum design of high-speed propellers.

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Acoustic Signal-Based Tunnel Incident Detection System (음향신호 기반 터널 돌발상황 검지시스템)

  • Jang, Jinhwan
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.18 no.5
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    • pp.112-125
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    • 2019
  • An acoustic signal-based, tunnel-incident detection system was developed and evaluated. The system was comprised of three components: algorithm, acoustic signal collector, and server system. The algorithm, which was based on nonnegative tensor factorization and a hidden Markov model, processes the acoustic signals to attenuate noise and detect incident-related signals. The acoustic signal collector gathers the tunnel sounds, digitalizes them, and transmits the digitalized acoustic signals to the center server. The server system issues an alert once the algorithm identifies an incident. The performance of the system was evaluated thoroughly in two steps: first, in a controlled tunnel environment using the recorded incident sounds, and second, in an uncontrolled tunnel environment using real-world incident sounds. As a result, the detection rates ranged from 80 to 95% at distances from 50 to 10 m in the controlled environment, and 94 % in the uncontrolled environment. The superiority of the developed system to the existing video image and loop detector-based systems lies in its instantaneous detection capability with less than 2 s.

Wind load estimation of super-tall buildings based on response data

  • Zhi, Lun-hai;Chen, Bo;Fang, Ming-xin
    • Structural Engineering and Mechanics
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    • v.56 no.4
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    • pp.625-648
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    • 2015
  • Modern super-tall buildings are more sensitive to strong winds. The evaluation of wind loads for the design of these buildings is of primary importance. A direct monitoring of wind forces acting on super-tall structures is quite difficult to be realized. Indirect measurements interpreted by inverse techniques are therefore favourable since dynamic response measurements are easier to be carried out. To this end, a Kalman filtering based inverse approach is developed in this study so as to estimate the wind loads on super-tall buildings based on limited structural responses. The optimum solution of Kalman filter gain by solving the Riccati equation is used to update the identification accuracy of external loads. The feasibility of the developed estimation method is investigated through the wind tunnel test of a typical super-tall building by using a Synchronous Multi-Pressure Scanning System. The effects of crucial factors such as the type of wind-induced response, the covariance matrix of noise, errors of structural modal parameters and levels of noise involved in the measurements on the wind load estimations are examined through detailed parametric study. The effects of the number of vibration modes on the identification quality are studied and discussed in detail. The made observations indicate that the proposed inverse approach is an effective tool for predicting the wind loads on super-tall buildings.

A study on pilot Test of the Composition Presplitting Angle Cut method in tunnel blasting (터널 심발부의 선균열을 이용한 발파공법의 현장시험에 관한 연구)

  • Hwang, Hak;Lee, Tai Ro
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.4 no.4
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    • pp.287-300
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    • 2002
  • Composition Presplitting Angle Cut (COPA-Cut) is a newly developed blasting method for tunnel excavation. Contrary to existing methods, COPA-Cut first creates presplitting by tension crack in cut. In this study, field tests measuring the advance efficiency, noise and ground vibration were performed in order to verify the presplitting effect. To compare the economy and workability, tests were simultaneously performed by COPA-Cut and existing method on the same condition. Results show that COPA-Cut increased advance efficiency and decreased noise and ground vibration. Also, it was confirmed that COPA-Cut is superior to existing method in terms of economy, workability and quality control.

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Features of the flow over a finite length square prism on a wall at various incidence angles

  • Sohankar, A.;Esfeh, M. Kazemi;Pourjafari, H.;Alam, Md. Mahbub;Wang, Longjun
    • Wind and Structures
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    • v.26 no.5
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    • pp.317-329
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    • 2018
  • Wake characteristics of the flow over a finite square prism at different incidence angles were experimentally investigated using an open-loop wind tunnel. A finite square prism with a width D = 15 mm and a height H = 7D was vertically mounted on a horizontal flat plate. The Reynolds number was varied from $6.5{\times}10^3$ to $28.5{\times}10^3$ and the incidence angle ${\alpha}$ was changed from $0^{\circ}$ to $45^{\circ}$. The ratio of boundary layer thickness to the prism height was about ${\delta}/H=7%$. The time-averaged velocity, turbulence intensity and the vortex shedding frequency were obtained through a single-component hotwire probe. Power spectrum of the streamwise velocity fluctuations revealed that the tip and base vortices shed at the same frequency as that ofspanwise vortices. Furthermore, the results showed that the critical incidence angle corresponding to the maximum Strouhal number and minimum wake width occurs at ${\alpha}_{cr}=15^{\circ}$ which is equal to that reported for an infinite prism. There is a reduction in the size of the wake region along the height of the prism when moving away from the ground plane towards the free end.

Stability Assessment of an Adjacent Ground Storage Tank by Blast-induced Vibration (발파진동에 대한 인접한 지상 저장탱크의 안정성 평가)

  • Jong, Yong-Hun;Lee, Chung-In;Choi, Yong-Kun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.1 s.106
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    • pp.19-26
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    • 2006
  • The test blasts were carried out by detonating some single blastholes at two upper sites of the underground storage cavern for the crude oil. One was performed at the entrance site of the construction tunnel and the other at the middle area of the underground storage cavern. Based on the blast-induced nitration measured by the test blasts, we suggested the propagation equations of blasting vibration that were capable of estimating the peak particle velocity. In addition, in order to assess the stability of the adjacent ground storage tank, we did the frequency analysis and the response spectrum analysis with the particle velocity-time history and the particle acceleration-time history that were measured by the test blast carried out on the entrance site of the construction tunnel. In result, it was predicted that the displacement on the highest part of the tank shell was less than the allowable displacement.

Crack Detection in Tunnel Using Convolutional Encoder-Decoder Network (컨볼루셔널 인코더-디코더 네트워크를 이용한 터널에서의 균열 검출)

  • Han, Bok Gyu;Yang, Hyeon Seok;Lee, Jong Min;Moon, Young Shik
    • Journal of the Institute of Electronics and Information Engineers
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    • v.54 no.6
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    • pp.80-89
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    • 2017
  • The classical approaches to detect cracks are performed by experienced inspection professionals by annotating the crack patterns manually. Because of each inspector's personal subjective experience, it is hard to guarantee objectiveness. To solve this issue, automated crack detection methods have been proposed however the methods are sensitive to image noise. Depending on the quality of image obtained, the image noise affect overall performance. In this paper, we propose crack detection method using a convolutional encoder-decoder network to overcome these weaknesses. Performance of which is significantly improved in terms of the recall, precision rate and F-measure than the previous methods.

A Case Study on the Stability Assessment of Structures by Blast-induced Vibration (발파진동에 대한 구조물 안정성 평가 - 지하비축기지 건설 사례)

  • Lee, Chung-In;Choi, Yong-Kun;Jong, Yong-Hun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.479-484
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    • 2005
  • The test blasts were carried out by detonating some single blastholes at two upper sites of the underground storage cavern the crude oil. One was performed at the entrance site of the construction tunnel and the other at the middle part of the underground storage cavern. Based on the blast-induced vibration measured by the test blasts, we suggested the propagation equations of blasting vibration that were capable of estimating the peak particle velocity. In addition, in order to assess the stability of the nearest ground storage tank, we did the frequency analysis and the response spectrum analysis with the particle velocity-time history and the particle acceleration-time history that were measured by the test blast carried out on the entrance site of the construction tunnel. In result, it was predicted that the displacement on the highest part of the tank shell was less than the allowable displacement.

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Next Generation Smart-City Facility Platform and Digital Chain (차세대 스마트도시 시설물의 플랫폼 정의와 디지털 체인)

  • Yang, Seung-Won;Kim, Jin-Wooung;Kim, Sung-Ah
    • Journal of KIBIM
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    • v.10 no.4
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    • pp.11-21
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    • 2020
  • With increasing interest and research on smart cities, there is also an increasing number of studies on urban facilities that can be built within smart cities. According to these studies, smart cities' urban facilities are likely to become high value-added industries. However, the concept of smart city is not clear because it involves various fields. Therefore, in this study, the definition of Next-Generation(N.G) Smart City Facilities with Digital Twin and Digital Chain is carried out through a multidisciplinary approach. Based on this, Next-Generation Smart City Facilities will be divided into High Value-Added Products and Big Data Platforms. Subsequently, the definition of the Digital Chain containing the data flow of the entire process built through the construction of the Digital Twin proceeds. The definitions derived are applied to the Next-Generation Noise Barrier Tunnel to ensure that data is exchanged at the Digital Twin stage, and to review the proposed configuration of the Digital Chain and Data Flow in this study. The platform definition and Digital Chain of Next-Generation Smart City Facilities proposed in this study suggest that it can affect not only the aspects of data management that are currently in the spotlight, but also the manufacturing industry as a whole.