95,421 research outputs found

    The First Spanish Short Wave Stations. Development of Radio & Tv Technology

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    In the thirties in Spain there were three big Short Wave Stations. One, belonging to Transradio Española in Aranjuez, 50 kilometers south of Madrid, which rendered radiotelegraphic services to the Canary Islands, Europe and America. Another, belonging to the Sociedad Anónima Radio Argentina (via Radiar), in Vallecas, on the outskirts of Madrid, also rendered radiotelegraphic services. The third belonged to the company Telefónica Nacional de España (CTNE), in Pozuelo del Rey, 50 kilometers east of Madrid provided radiotelephonic services to New York and Buenos Aires. In 1932, Aranjuez started broadcasting the programming of “EAQ-Madrid Radiodifusion Iberoamericana” directed to Spanish speaking countries. During the Civil War it became the Spanish Republican overseas broadcasting station. However, in 1937 as a result of the Battle of Jarama, Aranjuez became cut off from Madrid and the transmissions and call signs were transferred to the Vallecas transmitter EDZ using the call-sign EAQ-2

    Efficient harmonic oscillator chain energy harvester driven by colored noise

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    We study the performance of an electromechanical harmonic oscillator chain as an energy harvester to extract power from finite-bandwidth ambient random vibrations, which are modelled by colored noise. The proposed device is numerically simulated and its performance assessed by means of the net electrical power generated and its efficiency in converting the external noise-supplied power into electrical power. Our main result is a much enhanced performance, both in the net electrical power delivered and in efficiency, of the harmonic chain with respect to the popular single oscillator resonator. Our numerical findings are explained by means of an analytical approximation, in excellent agreement with numerics

    Leonard Baskin: Imaginary Artists

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    Leonard Baskin (1922-2000) was an American sculptor, illustrator, and printmaker. He is perhaps best known as a figurative sculptor and a creator of monumental woodcuts. The Gehenna Press, Baskin’s private press, operated for over 50 years (1942-2000) and produced more than 100 volumes of fine art books. His most prominent public commissions include sculpture for the Franklin Delano Roosevelt Memorial and the Woodrow Wilson Memorial, both in Washington D.C., and the Holocaust Memorial in Ann Arbor, MI. Baskin received numerous honors, among them a Guggenheim Fellowship, the Gold Medal of the National Academy of Arts and Letters, and the Jewish Cultural Achievement Award. He had many retrospective exhibitions, including those at the Smithsonian, the Albertina, and the Library of Congress. His work is in major private and public institutions, including the Metropolitan Museum of Art, the Museum of Modern Art, the Art Institute of Chicago, the British Museum, and the Vatican Museums. Imaginary Artists, a collection of 25 watercolor sketches, was completed in 1976 as a gift for Baskin’s friend, the distinguished Philadelphia lawyer Edwin Rome, and his wife, Rita. In this series Baskin skillfully acknowledges the Western art historical canon through irreverent references to traditional compositions and famous artists. His group of imaginary—or one can imagine uncredited—artists were often figured as the assistants, students, or rivals to the most noted painters of the centuries and include “Smedley Webb, little-known student of T. Eakins” and “Antonin du Colines, assistant to Poussin.” Through these representations, Baskin mirrors his earlier 1963 series Portraits of Artists, but takes up the subject, history, and medium of painting with humor and a serious commitment to figuration.https://cupola.gettysburg.edu/artcatalogs/1023/thumbnail.jp

    Boundary-layer turbulence in experiments of quasi-Keplerian flows

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    Most flows in nature and engineering are turbulent because of their large velocities and spatial scales. Laboratory experiments of rotating quasi-Keplerian flows, for which the angular velocity decreases radially but the angular momentum increases, are however laminar at Reynolds numbers exceeding one million. This is in apparent contradiction to direct numerical simulations showing that in these experiments turbulence transition is triggered by the axial boundaries. We here show numerically that as the Reynolds number increases turbulence becomes progressively confined to the boundary layers and the flow in the bulk fully relaminarizes. Our findings support that turbulence is unlikely to occur in isothermal constant density quasi-Keplerian flows.Comment: 16 pages, 8 figures. Accepted for publication in Journal of Fluid Mechanic

    Cyclic Lorentzian Lie Groups

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    We consider Lie groups equipped with a left-invariant cyclic Lorentzian metric. As in the Riemannian case, in terms of homogeneous structures, such metrics can be considered as different as possible from bi-invariant metrics. We show that several results concerning cyclic Riemannian metrics do not extend to their Lorentzian analogues, and obtain a full classification of three- and four-dimensional cyclic Lorentzian metrics
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