8,339 research outputs found
Accurate aeroacoustic measurements in closed-section hard-walled wind tunnels
No full textNoise emissions from aircraft are of major concern to aircraft manufacturers. There are various analytical, empirical and numerical tools to help in the design of quieter aircraft, however aeroacoustic measurements in wind tunnels are still required. There is a growing interest in simultaneous aerodynamic and aeroacoustic measurements in hard-walled closed-section wind tunnels. The research hypothesis of this work is whether accurate aeroacoustic measurements are possible in this type of wind tunnel. Two issues are of particular concern: the reverberation sound field and high background noise levels. De-reverberation, based on an Image Source Model (ISM), is proposed to tackle the first issue by incorporating the reflections in the focused beamformer. This technique is computationally fast and easy to implement. Source Power Integration and deconvolution techniques are shown to be still valid in de-reverberation. Measurements in a closed section wind tunnel have shown that an ISM gives a better estimate of the Green's functions, when compared to free-space Green's functions. Furthermore de-reverberation yielded more accurate source strength estimates from the beamformer. Qualitatively, de-convolved results were no different than when using free-space Green's functions. Simulations have shown that the ISM can become unstable at high frequencies if position errors are present. It is therefore recommended to limit the application of the ISM to frequencies below 10 kHz. At low frequencies the accuracy of beamforming levels is highly dependent on the level of noise contamination of the input data. Removing the diagonal of the cross spectral matrix might not be sufficient to eliminate this noise
J.C. Painter letter to Benjamin Lundy
No full textLetter from J.E. Painter to (presumably) Benjamin Lundy, answering a request for information about the history and operations of the Underground Railroad. Letter includes details of a story of an ex-slave transported on the Underground Railroad through Ohio and stories of the plight of other fugitive slaves crossing the Ohio River.
Benjamin Lundy (1789-1839) was a prominent Quaker abolitionist best known for his development of abolitionist periodicals. His "Genius of Universal Emancipation" was first published in 1821 from his home in Mt. Pleasant, Ohio, and enjoyed a wide circulation across the antebellum United States. In the 1820s, the young William Lloyd Garrison came to work for The Genius. Benjamin Lundy traveled widely seeking subscriptions to The Genius, giving talks about the anti-slavery movement, and observing and documenting the conditions of enslaved people across the Americas. He was also involved in the establishment of freed slave colonies in Mexico
SotonArray: Southampton University wind tunnel microphone array system guide
No full textThis report shall serve as an introductory background to SotonArray, the microphone array system at the University of Southampton. It covers the practical aspects only; namely the instrumentation setup and the beamforming software. It aims to give a basic level of understanding of the system to the researcher who wants to use it, and especially to highlight both the capabilities and limitations of the system. Since the microphone array system is a new capability for the Aerodynamics and Flight Mechanics research group (AFM), the hardware and software is constantly being upgraded, and the details given here are correct only at the time of going to print
Frequency response analysis of microphone preamplifiers in the audible and ultrasonic regime
No full textThis report presents an investigation on the frequency response of two types of electret microphone preamplifiers currently in use with SotonArray, Southampton University's wind tunnel microphone array system. The investigation is presented as a comparison between the response of an electret microphone coupled to the preamplifiers and a reference instrumentation-grade microphone and preamplifier assembly. The results show that electret microphones can potentially be used above their rated frequency range of 20kHz; in fact no degradation in signal was noticed up to 48kHz. The results also show that the newly-built SES preamps have a much better high-frequency performance than the original ISVR preamps
Mexican land grant contract to Benjamin Lundy, March 10, 1835 (English)
No full textLegal document from an unsigned officer to Benjamin Lundy, authorizing him rights as empresario to a tract of land in then-Mexico. The document extends a previous treaty made to Lundy by the government of Mexico from November 17, 1823 -- presumably, this land is to be the site of Lundy's freed slave colony. Original Spanish-language document is also a part of this collection. Benjamin Lundy (1789-1839) was a prominent Quaker abolitionist best known for his development of abolitionist periodicals. His Genius of Universal Emancipation was first published in 1821 from his home in Mt. Pleasant, Ohio, and enjoyed a wide circulation across the antebellum United States. In the 1820s, the young William Lloyd Garrison came to work for The Genius. Benjamin Lundy traveled widely seeking subscriptions to The Genius, giving talks about the anti-slavery movement, and observing and documenting the conditions of enslaved people across the Americas. He was also involved in the establishment of freed slave colonies in Mexico
Eli Nichols letter to Benjamin Lundy, March 17th, 1839
No full textFriendly note from Eli Nichols to Benjamin Lundy covering topics in contemporary abolition, ranging from the social status of abolitionists to the oppression of the poor. Much of the letter concerns a review of contemporary social movements in equality-based education, including Shaker and Quaker communities. The letter concludes in discussion of Nichols' and Lundy's interest in forming a freed slave colony or community in then-Mexico, and describes the climate and culture of those regions in detail. Benjamin Lundy (1789-1839) was a prominent Quaker abolitionist best known for his development of abolitionist periodicals. His Genius of Universal Emancipation was first published in 1821 from his home in Mt. Pleasant, Ohio, and enjoyed a wide circulation across the antebellum United States. In the 1820s, the young William Lloyd Garrison came to work for The Genius. Benjamin Lundy traveled widely seeking subscriptions to The Genius, giving talks about the anti-slavery movement, and observing and documenting the conditions of enslaved people across the Americas. He was also involved in the establishment of freed slave colonies in Mexico
Mexican land grant contract to Benjamin Lundy, March 10, 1835 (Spanish)
No full textLegal document in Spanish from the government of Tamaulipas, Mexico, to Benjamin Lundy, which appears to grant Lundy the rights of empresario for his proposed colony for freed slaves in Tamaulipas. This document appears to be truncated; it ends abruptly after 2 pages. Collection also includes a period translation of this contract with Lundy in English, which appears to contain the full text of the agreement. Benjamin Lundy (1789-1839) was a prominent Quaker abolitionist best known for his development of abolitionist periodicals. His Genius of Universal Emancipation was first published in 1821 from his home in Mt. Pleasant, Ohio, and enjoyed a wide circulation across the antebellum United States. In the 1820s, the young William Lloyd Garrison came to work for The Genius. Benjamin Lundy traveled widely seeking subscriptions to The Genius, giving talks about the anti-slavery movement, and observing and documenting the conditions of enslaved people across the Americas. He was also involved in the establishment of freed slave colonies in Mexico
General Benjamin Butler Letter Regarding the naming of Newport News, Virginia
No full textDigital images of an original letter written by Former Union Major-General Benjamin Butler in reply to a query by author, Edwin Everett Hale on how Newport News, Virginia had received it's name. both sides of the original letter are included along with a typed transcription of the letter
Cinq années de voyage en Orient 1846-1851 par Israel-Joseph Benjamin II, voyageur et auteur, demeurant à Faltischan (Moldavie). Paris en vente chez Michel Levy Frères, rue Vivienne, 2 bis 1856 L' auteur se réserve le droit de traduction et de reproduction
No full textPreface: by Benjamin, J.Dedication: by the author to M.J. Altaras aîné de Marseille et M. Albert Cohn.Content description: Detailed contentsPagination: PP28+240PVolumes: 1Text Genre:Pros
The description and use of an orrery of a new construction : representing in the various parts of its machinery all the motions and phoenomena [i.e phenomena] of the planetary system ...
No full textby Benjamin Marti
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