1 Introduction The science of sound in ducts can be traced back to the time when the sound wave equation was first derived.Many important ideas,concepts,and methods for acoustics were first developed for sound fields in ducts.Anyone with a little training in acoustics must be aware of normal specific acoustical impedance,the standing wave ratio,transmission line theory,and the cut-on frequencies of high-order wave-guide modes.In fact,duct acoustics has been so extensively taught
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机译:Ciclooxigenase-2 nos carcinoma carcinoma ductais de mama invasionivos com componente ductal in situ e noepitélioadjacente Cyclooxygenase-2 in invasive ductal carcinoma in ductal component in situ and related epithelium
机译:金属和非金属矿山安全和健康调查报告:地下非金属矿(石灰石(压碎和破碎))致命人员意外坠落,2014年2月27日,Interstate power systems,Inc。承包商I.D.位于爱荷华州story County ames的ames mine的martin marietta materials公司的T02号。矿山I.D.第13-00014号