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from article Precipitation (chemistry)
Precipitation of calcium fluoride. (Copyright © McGraw-Hill Education/Stephen Frisch)
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from article Active sound control
Results of a computer simulation of the sound field produced by two sources of spherical sound waves in air that have identical source strengths and are separated by a distance of 10 m. The sources are out of phase and radiate sound at a frequency…
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from article Active sound control
Feed-forward active noise control system. Elements of the system below the broken line are entirely digital, the filter H operating on the input sequence x to produce the output sequence y. The characteristics of the filter are designed by using the…
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from article Active sound control
Active control system for the suppression of propeller-induced aircraft cabin noise. The digital filters H1 and H2 are designed to minimize the sum of the squared error signals e1–e4.
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from article Active sound control
Distribution of sound pressure level (in decibels on an arbitrary scale) at head height in a 48-seat propeller aircraft (a) before and (b) after the use of a multichannel active noise control system consisting of 16 loudspeakers and 32 microphones.…
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from article Active sound control
Multichannel feed forward active control system for suppressing noise from multiple primary sources.
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from article Active sound control
Performance of a multichannel feed forward system for the active suppression of road-induced noise in a small passenger car at a speed of 60 km/h (37 mi/h). Reference signals were taken from six vibration sensors on the vehicle suspension. The…
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from article Deforestation
View of an area of deforestation in Central Kalimantan, Indonesia. In this case, the land is being cleared to develop areas for intensive rice production. (Credit: Australian National University)
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from article Deforestation
The relationship between forest and nonforest (other) land. Preservation of forest lands includes reforestation and natural regeneration. However, deforestation and natural events can lead to nonforest land. Afforestation (the act or process of…
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from article Deforestation
Natural forest areas (in hectares; 1 hectare = 2.47 acres) in various climatic domains (boreal/polar, temperate, subtropical, and tropical) from 1990 to 2015. The data are derived from the Global Forest Resources Assessment 2015 by the Food and…
