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문성필,김재필 한국목재공학회 1994 목재공학 Vol.22 No.1
Effects of Mg - base acid sulfite and Mg- or Na-base bisulfite on pine bark cooking were examined. In the presence of 75% free acid at 145℃, the rate of cooking and delignification was improved with the increase of total acid. However, the delignification could not be achieved by 50% or more under these cooking conditions. When cooked with 50∼65℃ free acid and at 155∼165℃, the rate of cooking and delignification was remarkably improved. Thus, the bark was delignified up to 73% when cooked for 2 hours in the presence of 50% free acid and 24% total acid. Na-base bisulfite was slightly more effective than Mg-base bisulfite for cooking, giving 76 delignification of pine bark. However, there was no significant difference in selectivity of delignification between Na- and Mg-base bisulfite cooking.
Feedback Active Noise Control Based Voice Enhancing Ear-Protection System
문성필,장태규 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.4
This paper proposes a voice enhancing ear-protection system which is based on feedback active noise control(FBANC). The proposed system selectively suppresses the background noise and preserves the talking voice by controlling the adaptive algorithm with the voice activity period detection module. The noise reduction performance of the proposed noise canceling algorithm is analytically derived for the two key performance affecting parameters, i.e., electro-acoustic coupling distance and noise bandwidth. The proposed system is also implemented with a floating-point DSP system and its performance is experimentally tested to compare with the analytically derived results. The achieved levels of noise reduction for the three different noise bandwidths cases, i.e., 10Hz, 50Hz, and 90Hz, are high to show 17.05dB, 10.54dB and 8.99dB, respectively. The feasibility of the proposed system is also shown by the peak noise reduction achieved more than 25dB while preserving the voice component in the frequency range between 200-800Hz.