vocal cord

Either of two folds of mucous membrane that extend across the interior cavity of the larynx and are primarily responsible for voice production. Sound is produced by the vibration of the folds in response to the passage between them of air exhaled from the lungs. The pitch of sound varies with the degree of vocal-cord tension. Sounds are then modified by the tongue, palate, and lips to produce speech. When at rest, the vocal cords lie apart, forming a V-shaped opening (glottis) through which air is breathed. The folds located just above the vocal cords are termed the vestibular or false vocal cords because they are not involved in voice production. Inflammation (as from excessive use) limits the normal contraction of the vocal cords, resulting in hoarseness.

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In geology, an undulation or wave in the stratified rocks of the Earth's crust. Stratified rocks were originally formed from sediments that were deposited in flat, horizontal sheets, although in some places the strata are no longer horizontal but have warped. The warping may be so gentle that the inclination of the strata is barely perceptible, or it may be so pronounced that the strata of the two flanks are essentially parallel or nearly flat. Folds vary widely in size; the tops of large folds are commonly eroded away on the Earth's surface.

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The Miura-fold is a rigid fold that has been used to simulate large solar panel arrays for space satellites in the Japanese 1995 Space Flight Unit. It was invented by Japanese astrophysicist Koryo Miura. It is an example of the practical importance of rigid origami, or treating hinges and rigid surfaces like the paper and creases in paper folding problems.

A folded Miura-fold can be packed into an area no larger than the size of one of the segments that make up the overall shape, its thickness restricted only by the thickness of the folded material.

The fold can also be unpacked in just one motion by pulling on opposite ends of the folded material, and likewise folded again by pushing the two ends back together. This was beneficial to the aforementioned solar array as it reduced the number of motors required to unfold it, reducing the overall weight and complexity of the mechanism.


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