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05. %EA%B8%B0%EB%B0%80%EC%84%B1%EC%9D%84 %EA%B0%9C%EC%84%A0%ED%95%98%EA%B8%B0 %EC%9C%84%ED%95%9C %EC%9D%BC%EB%B0%98%EC%9B%90%EC%B9%99%28General principles for improving airtightness%29