11,199 research outputs found
Helicopter main-rotor speed effects: A comparison of predicted ranges of detection from the aural detection program ICHIN and the electronic detection program ARCAS
NASA LaRC personnel have conducted a strudy of the predicted acoustic detection ranges associated with reduced helicopter main rotor speeds. This was accomplished by providing identical input information to both the aural detection program ICHIN 6, (I Can Hear It Now, version 6) and the electronic acoustic detection program ARCAS (Assessment of Rotorcraft Detection by Acoustics Sensing). In this study, it was concluded that reducing the main rotor speed of the helicopter by 27 percent reduced both the predicted aural and electronic detection ranges by approximately 50 percent. Additionally, ARCAS was observed to function better with narrowband spectral input than with one-third octave band spectral inputs and the predicted electronic range of acoustic detection is greater than the predicted aural detection range
More Power to You
"Anyone interested in the Bonneville Power project will find much valuable data in this folio volume.
Early Catholic Missions in Old Oregon, Volume II. Edited by Clarence B. Bagley
"The present and concluding volume contains a translation into the English language of the rare Notice sur le Territoire et sur la Mission de l'Oregon (Bruxelles, 1847).
Handbook of Learned Societies and Institutions: America
"One of the first projects approved by the trustees of the Carnegie Institution was the publication of a handbook of learned societies, this being regarded as a necessary preparation to almost any kind of careful research.
Bibliography of American Historical Societies
"The work as now issued is easily the most important one volume bibliography in the field of American history.
Early Library Development in Washington
"In the fifty years that have elapsed since 1876, great progress in Washington has been inevitable. That progress has been almost wholly confined, however, to the period since Statehood… The notes prepared for this paper have been purposely confined to the Territorial period, 1853-1889.
Adventures in Alaska and Along the Trail
"Three new volumes received by this Quarterly since the last issue was printed indicates a continuing interest in Alaska and the Northland.
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