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시속 200㎞급 고속철도차량의 공조시스템 소음저감기술개발
박철희(Chol-Hui Pak),이우식(U. Lee),주재만(JaeMan Joo),김주홍(Joohong Kim) 한국철도학회 1998 한국철도학회 학술발표대회논문집 Vol.- No.-
This study represents the technique about the noise reduction of HVAC equipment for high speed train(HST) operating at 200 ㎞/h. HST is different from the low speed train in the various points as well as the speed. Especially, the noise of cabin is closely related to the comfort of passenger and the noise from HVAC is one of main noise source in the cabin. In this study, the noise from HVAC was reduced by 5 ㏈(A)" using the concept of multiple resonator and guide vein. Therefore, the noise of cabin decreased from 60 ㏈(A) to 55 ㏈(A) at the center of the cabin.
New Approach to 1:1 and 3:1 Internal Resonances
Chol Hui Pak(박철희) 한국소음진동공학회 2017 한국소음진동공학회 논문집 Vol.27 No.7
The motions are not necessarily assumed to be small, nor the ratio of the linearized natural frequency is close to 1 or 3. When a two-degree-of-freedom cubic nonlinear system is weakly damped and under a small sinusoidal force applied on one mode, it is observed that if the driving mode loses stability in the underlying conservative system then a stable coupled-mode response is generated. Based on this observation, the coupled-mode responses are computed in the systems having 1:1 and 3:1 internal resonances, and the responses are compared with those obtained by using the multiple scale perturbation technique. The system is classified into two groups; simple and general. A simple system is symmetric with respect to both coordinates, including two-mode model of nonlinear continuous systems. It is found in simple systems having 1:1 internal resonance that the coupled-mode response obtained by using the perturbation technique is agreeable with that by the proposed method, but an unreasonable result is found in general systems. Moreover, unreasonable results are found in the systems (simple and general) having 3:1 internal resonance. For these systems, procedures are formulated to compute the coupled-mode responses by using the harmonic balance method with the functional form of two-term approximation (that is, at least one coordinate is expressed by two harmonic terms). The origin of the discrepancy between the perturbation technique and the proposed method is briefly discussed.