59 résultats pour "vibrations"
- Vue de la faille de San Andréas.
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Sound
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INTRODUCTION
Sound, physical phenomenon that stimulates the sense of hearing.
A fundamental law of harmony states that two notes an octave apart, when sounded together, produce a pleasant-sounding combination. Other combinations of notescan also be pleasing. Physically, an interval of a fifth consists of two notes, the frequencies of which bear the arithmetical ratio 3 to 2, and a major third, the ratio 5 to4. Fundamentally, the law of harmony states that two or more notes sound pleasant when played together if their frequencies bear small, whole number ratios; if thefreq...
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Musical Instruments
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INTRODUCTION
World Music Tour
Click on the instruments to hear music from around the world.
Traditional Timbila of MozambiqueAmong the Chopi, who have lived for centuries along the coast of Mozambique, there is a highly developed tradition ofsongwriting and composing for timbila (xylophone) orchestras. Elaborate migodo (dance suites), interspersed with poeticsongs pertaining to village life, are often performed to these compositions. Timbila music is now recognized as the nationalmusic of Mozambique."Eduardo Durao Mauaia" from Eduardo Durao and Orquestra Durao: Timbila (Cat.# Globestyl...
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supraconductivité.
vitesses des électrons s'organisent, chaque paire étant formée de deux électrons dont les vitesses sont strictement opposées ; l'ordre n'est apparent que dans l'espace des moments et pas dans l'espace réel des positions comme c'est le cas, pour les atomes, d'un cristal de glace. Les supraconducteurs peuvent transporter des courants de forte intensité sans dissipation de chaleur, d'où des applications à forte densité de courant (bobines créant des champs magnétiques intenses, cavités...
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spectroscopie - astronomie.
La dispersion de la lumière est réalisée dans ce cas par un réseau de diffraction et non par un prisme. Ce réseau est constitué d'un miroir en verre ou en métal, sur lequelont été gravées un grand nombre de lignes parallèles. L'emploi d'un miroir concave qui focalise alors la lumière évite de munir le spectroscope de lentilles. Un spectroscopeà réseau offre un spectre plus détaillé qu'un spectroscope à prisme, car un réseau possède un pouvoir dispersif bien plus important. 3.3 Spectrographe Le...
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Snake (reptile).
in their heads that conduct sound. They are able to hear low-frequency sounds and to sense vibrations that travel through the ground or water. The majority of snakeshave good eyesight, especially for detecting moving objects, although most burrowing snakes can only distinguish between light and dark. Pit vipers, boas, and pythons have an unusual adaptation for detecting warm-blooded prey and predators. On the heads of these snakes are small pits lined with cellsthat are extremely sensitive to he...
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Turtle.
Turtles use their jaws to cut and handle food. Instead of teeth, a turtle’s upper and lower jaws are covered by horny ridges, similar to a bird’s beak. Meat-eating turtlescommonly have knife-sharp ridges for slicing through their prey. Plant-eating turtles often have ridges with serrated edges that help them cut through tough plants.Turtles use their tongues in swallowing food, but unlike many other reptiles, such as chameleons, they cannot stick out their tongues to capture food. C Limb Structu...
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Turtle - biology.
Turtles use their jaws to cut and handle food. Instead of teeth, a turtle’s upper and lower jaws are covered by horny ridges, similar to a bird’s beak. Meat-eating turtlescommonly have knife-sharp ridges for slicing through their prey. Plant-eating turtles often have ridges with serrated edges that help them cut through tough plants.Turtles use their tongues in swallowing food, but unlike many other reptiles, such as chameleons, they cannot stick out their tongues to capture food. C Limb Structu...
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Les sonars
longueur d'onde émise , une basse fréquence impliquerait un émetteur encombrant Comme toujours , il faut donc établir un compromis entre la portée , la résolution et l'encombrement Et cela conduit à une préférence des ultrasons. Reste à savoir comment produire des vibrations de si hautes fréquences ? Plusieurs techniques électro-acoustiques permettent cela dans les sonars artificiels : principalement les transducteurs piézoélectriques et les transduct...