• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.422-428
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• 2018

Increase in use of lightweight structures, coupled with the increased acoustic loads resulting from larger and longer range guided missiles, has made missile more susceptible to failures caused by acoustic loads. Thus, accurate prediction of acoustic environment and the response is becoming ever more important for mission success. In this paper, the acoustic response of a sandwich composite skin structure to diffuse acoustic excitation is predicted over a broad frequency range. For the low frequency acoustic analysis, coupled FE-BEM method is used where the structure is modeled using FEM and the interior and exterior fluid is modeled using BEM. For the high frequency region, statistical energy analysis is applied. The predicted acoustic level inside the structure is compared with the result from acoustic test conducted in reverberation chamber, which shows very good agreement.

• Journal of ILASS-Korea
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• v.29 no.1
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• pp.23-31
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• 2024

This study conducted a 3D thermo-acoustic analysis based on the helmholtz solver to analyze the major resonance modes causing combustion instability in a single-can combustor. The experimental investigations were carried out on a test rig designed by the Korea Institute of Machinery & Materials (KIMM) under various conditions of hydrogen co-firing and fuel staging. Through these experiments, two primary unstable frequencies were identified. To determine the resonance modes of these frequencies, a 3D thermo-acoustic analysis was conducted using temperature information from the test rig. The results confirmed that the unstable frequencies observed in the experiments were all longitudinal modes. Additionally, the mode shapes identified in the analysis facilitated a simplification of the exit geometry for the low-order network model, confirming that this did not significantly affect the fundamental resonance modes.

• MALSORI
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• no.44
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• pp.47-59
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• 2002

Mean F0, Jitter, Shimmer, and NHR were measured in 21 opera singers, 13 Korean traditional 'pansori' singers, and 21 non-singers. Four voice sampling conditions were ordinary /α/ prolongation, /α/ prolongation using vocal technique as if the subjects were singing, oral reading of the words of a song, and singing. One-way ANOVA and Sheffe post-hoc analysis were used to identify significant differences among the groups. The mean F0 was significantly different among the 3 groups in all conditions except for the ordinary /α/ prolongation condition. The opera singers produced lower jitter and NHR compared to 'pansori' singers and non-singers only in the singing condition.