• Journal of KSNVE
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• v.8 no.1
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• pp.146-156
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• 1998

To mitigate excessive noise from highways, and high speed rail road, it is often necessary to construct a noise barrier. Absorptive barroer attenuation solution is obtained for the problem of diffration of a plane wave sound source by a semi-infinite plane. A finite region in the vicinity of the edge has an highly absorbing boundary condition ; the remaining portion of the half plane is rigid. The problem which is solved is a mathematical model for a hard barrier with an absorbing edge. If the wavelength of the sound is much smaller than the length scale associated with the barrier, the diffraction process is governed to all intents and purpose by the solution to a standard problem of diffraction by a semi-infinite hard plane with an absorbent edge. It is concluded that the absorbing material that comprises the edge need only be of the order of a wavelength long to have approximately the same effect, on the sound attenuation in the shadow side of the barrier. Traffic noise is composed of thousands of sources with varying frequency content. To simplify noise predictions when barriers are present, an effective frequency of 550Hz may be used to represent all vehicles. The wavelength of sound at f=550Hz for traffic noise is about 2 feet. According to the above conclusion, an absorptive highway noise barrier is only needed to cover to cover approximately a 2 foot length of absorbing material. It would be more economical to cover only the region in the immediate vicinity of the edge with highly sound obsorbent material.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.722-728
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• 2017

As the demand for high-speed railway, light railway, and metropolitan railway is increasing, the demand for safe and comfortable railways is increasing. The evaluation technology for a railway system manufactured according to this trend is becoming more important. This study examined the domestic and foreign technology trends through patent analysis of the railway test technology. To accomplish this, the patents filed in Korea, Europe, and the United States since 1990 were analyzed using Thomson Innovation DB. First, the technology was classified as a component test, combined test, and on-line test. Through patent analysis, the technology trends in the railway test technology and how the technological progress has been made from the past to the present were reviewed. In addition, through an analysis of the country and main applicant, this study examined the countries and applicants that are actively developing technologies. In addition, the countries that have secured technology related to the test technology were studied through an analysis of the market security index and the influence index. Through this analysis, this study analyzed the trend of the test technology in the railway area.