Commit b9d63285 authored by Claude Meny's avatar Claude Meny

Update cheatsheet.en.md

parent b7100335
Pipeline #22188 canceled with stage
...@@ -80,33 +80,34 @@ of the pond. ...@@ -80,33 +80,34 @@ of the pond.
* A field is **uniform** if *its value is the same at every point* in space at a given * A field is **uniform** if *its value is the same at every point* in space at a given
instant or over a specified time period. instant or over a specified time period.
<br> <br>
_*Example:* Even without ripples, the depth of a pond varies from one point to another._ _For example, even without ripples, the depth of a pond varies from one point to another._
_The water height field beneath the surface is **not uniform**._ _The water height field beneath the surface is not uniform._
_*However,* in an Olympic swimming pool where the water depth is the same everywhere,_ _However, in an Olympic swimming pool where the water depth is the same everywhere,_
_the water height field **is uniform** at the surface._ _the water height field is uniform at the surface._
* A field is **stationary** if *its values*—which may vary in space—*do not change over time*. * A field is **stationary** if *its values*—which may vary in space—*do not change over time*.
_*Example:* In a calm, windless pond where the water surface is "at rest," perfectly still,_ <br>
_the water height field is **stationary**._ _In a calm, windless pond where the water surface is "at rest," perfectly still,_
_the water height field is stationary._
* A field is **homogeneous** if *its propagation properties* (the shape of the perturbation * A field is **homogeneous** if *its propagation properties* (the shape of the perturbation
for a given impact and its propagation speed in a given direction) *are identical at every point* for a given impact and its propagation speed in a given direction) *are identical at every point*
in space, even if the field’s values vary spatially. in space, even if the field’s values vary spatially.
<br> <br>
_*Example:* The speed of ripples depends on depth—shallow water slows propagation due to friction_ _The speed of ripples depends on depth—shallow water slows propagation due to friction_
_with the bottom, while deep water allows faster wave movement._ _with the bottom, while deep water allows faster wave movement._
_*Thus,* since a pond’s depth varies, its water height field is **not strictly homogeneous**._ _Thus, since a pond’s depth varies, its water height field is not strictly homogeneous._
_*However,* in an Olympic pool with constant depth, the field **is homogeneous**._ _However, in an Olympic pool with constant depth, the field is homogeneous._
* A field is **isotropic** if, regardless of the impact point, *the propagation of the perturbation* * A field is **isotropic** if, regardless of the impact point, *the propagation of the perturbation*
(its speed, shape, and attenuation) *does not depend on direction*, even if the (its speed, shape, and attenuation) *does not depend on direction*, even if the
induced perturbation varies from one point to another for the same impact. induced perturbation varies from one point to another for the same impact.
<br> <br>
_*Example:* If raindrops in a pond always create perfectly circular ripples that propagate_ _If raindrops in a pond always create perfectly circular ripples that propagate_
_outward, it means each ripple spreads at the same speed in all directions._ _outward, it means each ripple spreads at the same speed in all directions._
_*Furthermore,* if the height of a ripple remains constant at equal distances from_ _Furthermore, if the height of a ripple remains constant at equal distances from_
_the impact point, then the water height field is **isotropic**._ _the impact point, then the water height field is isotropic._
* A field is **linear** if, for a point-like and instantaneous impact, * A field is **linear** if, for a point-like and instantaneous impact,
*the amplitude of the perturbation is proportional to the energy of the impact*, *the amplitude of the perturbation is proportional to the energy of the impact*,
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